We are running odoo 9 community version, and after a while of using it, it stop works. All menus are not shown after login. Only web page is accessible (without admin functionality). This is the only error from log which might be related. I assume there is some user reference data stored here. Can anyone help me to figure it out? how to get all users work again and how to prevent this issue?

2015-10-19 15:08:34,272 7734 INFO eko-prod openerp.addons.base.ir.ir_attachment: _read_file reading /var/lib/odoo/filestore/eko-prod/97/97879b37e66639d695f6f61c40d7ec9b695d2cc3
Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/openerp/addons/base/ir/ir_attachment.py", line 151, in _file_read
    r = open(full_path,'rb').read().encode('base64')
IOError: [Errno 2] No such file or directory: u'/var/lib/odoo/filestore/eko-prod/97/97879b37e66639d695f6f61c40d7ec9b695d2cc3'