Odoo v8

Under: Edit Company Data > Report Configuration > Configuration (RML)  

When trying to preview Header/footer I am having this problem: 

Odoo Client Error
Uncaught SyntaxError: Unexpected end of input

When looking at the log:

2014-09-30 14:19:10,662 1417 ERROR testrcl openerp.addons.web.controllers.main: An exception occured during an http request
Traceback (most recent call last):
  File "/opt/odoo/openerp/addons/web/controllers/main.py", line 69, in wrap
    return f(*args, **kwargs)
  File "/opt/odoo/openerp/addons/web/controllers/main.py", line 1570, in index
    request.session.db, request.session.uid, request.session.password, report_id)
  File "/opt/odoo/openerp/http.py", line 807, in proxy_method
    result = dispatch_rpc(self.service_name, method, args)
  File "/opt/odoo/openerp/http.py", line 100, in dispatch_rpc
    result = dispatch(method, params)
  File "/opt/odoo/openerp/service/report.py", line 34, in dispatch
    res = fn(db, uid, *params)
  File "/opt/odoo/openerp/service/report.py", line 141, in exp_report_get
    return _check_report(report_id)
  File "/opt/odoo/openerp/service/report.py", line 119, in _check_report
    raise openerp.osv.orm.except_orm(exc.message, exc.traceback)
except_orm: ('RML is not available at specified location or not enough data to print!', (None, None, None))

Furthermore,I have checked that the fonts used are installed in my server and wkhtmltopdf is working properly. But, am I missing a library, a configuration or something?.