I just updated some packages of my Ubuntu server (nothing OpenERP related as far as I can tell) and rebooted it as there were also some kernel updates. After that I saw "No handler found." when I went to the webinterface of my OpenERP installation. Having a look in my openerp-server.log I saw "openerp.modules.module: Couldn't load module web". I guess that's responsible for the "No handler found" message but why the heck couldn't it load the web module?? OpenERP was running just fine for several month now and survived many system updates and reboots (I excluded OpenERP itself from the apt-get update routine as I don't like the idea of getting a untested nightly version every day...). And there was nothing changed, I checked the addons path (correct and all web and web_* directories in place), I checked the file permissions and ownership (correct and openerp may still access and modify all of its files) and I checked if some file would have been modified lately (not the case).

After those checks I played a little around with the addons path and updated openerp manually to the latest nightly version. This didn't change anything.

So what can I do?

Here is the log file with my original OpenERP version and after the update. I also tried debug mode but that didn't reveal anything more useful than that. I also guess the "report.sale.order"-problem you see in the log has nothing to do with the problem also I'm not sure and I wouldn't know how to fix it:

2014-02-05 17:34:07,124 32862 INFO ? openerp: OpenERP version 7.0-20131016-232725
2014-02-05 17:34:07,124 32862 INFO ? openerp: addons paths: /usr/lib/pymodules/python2.7/openerp/addons
2014-02-05 17:34:07,124 32862 INFO ? openerp: database hostname: localhost
2014-02-05 17:34:07,124 32862 INFO ? openerp: database port: 5432
2014-02-05 17:34:07,124 32862 INFO ? openerp: database user: openerp
2014-02-05 17:34:07,495 32862 INFO ? openerp.addons.google_docs.google_docs: GData lib version `%s GData-Python/2.0.14` detected
2014-02-05 17:34:07,705 32862 CRITICAL ? openerp.modules.module: Couldn't load module web
2014-02-05 17:34:07,705 32862 CRITICAL ? openerp.modules.module: The report "report.sale.order" already exists!
2014-02-05 17:34:07,705 32862 ERROR ? openerp.service: Failed to load server-wide module `web`.
The `web` module is provided by the addons found in the `openerp-web` project.
Maybe you forgot to add those addons in your addons_path configuration.
Traceback (most recent call last):
  File "/usr/lib/pymodules/python2.7/openerp/service/__init__.py", line 60, in load_server_wide_modules
    openerp.modules.module.load_openerp_module(m)
  File "/usr/lib/pymodules/python2.7/openerp/modules/module.py", line 415, in load_openerp_module
    getattr(sys.modules['openerp.addons.' + module_name], info['post_load'])()
  File "/usr/lib/pymodules/python2.7/openerp/addons/web/http.py", line 628, in wsgi_postload
    openerp.wsgi.register_wsgi_handler(Root())
  File "/usr/lib/pymodules/python2.7/openerp/addons/web/http.py", line 517, in __init__
    self.load_addons()
  File "/usr/lib/pymodules/python2.7/openerp/addons/web/http.py", line 580, in load_addons
    m = __import__('openerp.addons.' + module)
  File "/usr/lib/pymodules/python2.7/openerp/modules/module.py", line 133, in load_module
    mod = imp.load_module('openerp.addons.' + module_part, f, path, descr)
  File "/usr/lib/pymodules/python2.7/openerp/addons/sale~1/__init__.py", line 29, in <module>
    import report
  File "/usr/lib/pymodules/python2.7/openerp/addons/sale~1/report/__init__.py", line 22, in <module>
    import sale_order
  File "/usr/lib/pymodules/python2.7/openerp/addons/sale~1/report/sale_order.py", line 42, in <module>
    report_sxw.report_sxw('report.sale.order', 'sale.order', 'addons/sale/report/sale_order.rml', parser=order, header="external")
  File "/usr/lib/pymodules/python2.7/openerp/report/report_sxw.py", line 392, in __init__
    report_rml.__init__(self, name, table, rml, '')
  File "/usr/lib/pymodules/python2.7/openerp/report/interface.py", line 65, in __init__
    super(report_rml, self).__init__(name)
  File "/usr/lib/pymodules/python2.7/openerp/report/interface.py", line 45, in __init__
    assert not self.exists(name), 'The report "%s" already exists!' % name
AssertionError: The report "report.sale.order" already exists!
2014-02-05 17:34:07,713 32862 INFO ? openerp.service.wsgi_server: HTTP service (werkzeug) running on 0.0.0.0:8069
2014-02-05 17:34:07,713 32862 INFO ? openerp: OpenERP server is running, waiting for connections...
2014-02-05 17:36:04,779 32862 INFO ? openerp.service: Initiating shutdown
2014-02-05 17:36:04,779 32862 INFO ? openerp.service: Hit CTRL-C again or send a second signal to force the shutdown.
2014-02-05 17:37:35,084 33110 INFO ? openerp: OpenERP version 7.0-20140205-002759
2014-02-05 17:37:35,085 33110 INFO ? openerp: addons paths: /usr/lib/pymodules/python2.7/openerp/addons,/usr/share/pyshared/openerp/addons
2014-02-05 17:37:35,085 33110 INFO ? openerp: database hostname: localhost
2014-02-05 17:37:35,085 33110 INFO ? openerp: database port: 5432
2014-02-05 17:37:35,085 33110 INFO ? openerp: database user: openerp
2014-02-05 17:37:35,445 33110 INFO ? openerp.addons.google_docs.google_docs: GData lib version `%s GData-Python/2.0.14` detected
2014-02-05 17:37:35,756 33110 CRITICAL ? openerp.modules.module: Couldn't load module web
2014-02-05 17:37:35,756 33110 CRITICAL ? openerp.modules.module: The report "report.sale.order" already exists!
2014-02-05 17:37:35,756 33110 ERROR ? openerp.service: Failed to load server-wide module `web`.
The `web` module is provided by the addons found in the `openerp-web` project.
Maybe you forgot to add those addons in your addons_path configuration.
Traceback (most recent call last):
  File "/usr/lib/pymodules/python2.7/openerp/service/__init__.py", line 60, in load_server_wide_modules
    openerp.modules.module.load_openerp_module(m)
  File "/usr/lib/pymodules/python2.7/openerp/modules/module.py", line 415, in load_openerp_module
    getattr(sys.modules['openerp.addons.' + module_name], info['post_load'])()
  File "/usr/lib/pymodules/python2.7/openerp/addons/web/http.py", line 628, in wsgi_postload
    openerp.wsgi.register_wsgi_handler(Root())
  File "/usr/lib/pymodules/python2.7/openerp/addons/web/http.py", line 517, in __init__
    self.load_addons()
  File "/usr/lib/pymodules/python2.7/openerp/addons/web/http.py", line 580, in load_addons
    m = __import__('openerp.addons.' + module)
  File "/usr/lib/pymodules/python2.7/openerp/modules/module.py", line 133, in load_module
    mod = imp.load_module('openerp.addons.' + module_part, f, path, descr)
  File "/usr/lib/pymodules/python2.7/openerp/addons/sale~1/__init__.py", line 29, in <module>
    import report
  File "/usr/lib/pymodules/python2.7/openerp/addons/sale~1/report/__init__.py", line 22, in <module>
    import sale_order
  File "/usr/lib/pymodules/python2.7/openerp/addons/sale~1/report/sale_order.py", line 42, in <module>
    report_sxw.report_sxw('report.sale.order', 'sale.order', 'addons/sale/report/sale_order.rml', parser=order, header="external")
  File "/usr/lib/pymodules/python2.7/openerp/report/report_sxw.py", line 390, in __init__
    report_rml.__init__(self, name, table, rml, '')
  File "/usr/lib/pymodules/python2.7/openerp/report/interface.py", line 65, in __init__
    super(report_rml, self).__init__(name)
  File "/usr/lib/pymodules/python2.7/openerp/report/interface.py", line 45, in __init__
    assert not self.exists(name), 'The report "%s" already exists!' % name
AssertionError: The report "report.sale.order" already exists!
2014-02-05 17:37:35,766 33110 INFO ? openerp.service.wsgi_server: HTTP service (werkzeug) running on 0.0.0.0:8069
2014-02-05 17:37:35,767 33110 INFO ? openerp: OpenERP server is running, waiting for connections...
2014-02-05 17:38:52,180 33110 INFO ? werkzeug: 10.0.2.5 - - [05/Feb/2014 17:38:52] "GET / HTTP/1.1" 404 -
2014-02-05 17:46:21,240 33110 INFO ? openerp.service: Initiating shutdown
2014-02-05 17:46:21,241 33110 INFO ? openerp.service: Hit CTRL-C again or send a second signal to force the shutdown.