Today I wanted to update the databases of my odoo 8 projects. But I get errors and I don't know how I can fix this.

This is the log while the update procedure:

  File "/opt/odoo/odoo-server/openerp/api.py", line 235, in wrapper
    return old_api(self, *args, **kwargs)
  File "/opt/odoo/odoo-server/openerp/addons/base/ir/ir_ui_view.py", line 206, in _check_xml
    view_def = self.read_combined(cr, uid, view.id, None, context=context)
  File "/opt/odoo/odoo-server/openerp/api.py", line 235, in wrapper
    return old_api(self, *args, **kwargs)
  File "/opt/odoo/odoo-server/openerp/addons/base/ir/ir_ui_view.py", line 552, in read_combined
    cr, uid, arch_tree, root_id, base.model, context=context)
  File "/opt/odoo/odoo-server/openerp/api.py", line 235, in wrapper
    return old_api(self, *args, **kwargs)
  File "/opt/odoo/odoo-server/openerp/addons/base/ir/ir_ui_view.py", line 504, in apply_view_inheritance
    source = self.apply_inheritance_specs(cr, uid, source, specs_tree, view_id, context=context)
  File "/opt/odoo/odoo-server/openerp/api.py", line 235, in wrapper
    return old_api(self, *args, **kwargs)
  File "/opt/odoo/odoo-server/openerp/addons/base/ir/ir_ui_view.py", line 482, in apply_inheritance_specs
    self.raise_view_error(cr, uid, _("Element '%s' cannot be located in parent view") % tag, inherit_id, context=context
)
  File "/opt/odoo/odoo-server/openerp/api.py", line 235, in wrapper
    return old_api(self, *args, **kwargs)
  File "/opt/odoo/odoo-server/openerp/addons/base/ir/ir_ui_view.py", line 367, in raise_view_error
    raise AttributeError(message)
AttributeError: Element '<xpath expr="//link[@id='bootstrap_css']">' cannot be located in parent view

Error context:
View `Cerulean`
[view_id: 295, xml_id: website.theme_cerulean, model: n/a, parent_id: 255]

When I restart the server an want to swtich to the site with the updated DB I get:

2014-09-08 08:36:49,210 1572 ERROR koina-ag openerp.addons.base.ir.ir_ui_view: Element '<xpath expr="//link[@id='bootstrap_css']">' cannot be located in parent view

Error context:
View `Cerulean`
[view_id: 400, xml_id: website.theme_cerulean, model: n/a, parent_id: 360]
2014-09-08 08:36:49,216 1572 INFO koina-ag werkzeug: 192.168.188.20 - - [08/Sep/2014 08:36:49] "GET /web?db=koina-ag HTTP/1.1" 302 -

In the database in line 400 of  ir.ir_ui_view I can't find any signicant difference between a fresh installed an working site and the defect site.