I get this error whenever i try to click on cutomers: ValueError: invalid literal for int() with base 10: 'False' Full error details:

Server Traceback (most recent call last):
  File "C:\Program Files\OpenERP 6.1-1\server\openerp\addons\web\common\http.py", line 592, in send
  File "C:\Program Files\OpenERP 6.1-1\server\.\openerp\netsvc.py", line 360, in dispatch_rpc
  File "C:\Program Files\OpenERP 6.1-1\server\.\openerp\service\web_services.py", line 572, in dispatch
  File "C:\Program Files\OpenERP 6.1-1\server\.\openerp\osv\osv.py", line 167, in execute_kw
  File "C:\Program Files\OpenERP 6.1-1\server\.\openerp\osv\osv.py", line 121, in wrapper
  File "C:\Program Files\OpenERP 6.1-1\server\.\openerp\osv\osv.py", line 176, in execute
  File "C:\Program Files\OpenERP 6.1-1\server\.\openerp\osv\osv.py", line 164, in execute_cr
  File "C:\Program Files\OpenERP 6.1-1\server\.\openerp\osv\orm.py", line 2165, in fields_view_get
  File "C:\Program Files\OpenERP 6.1-1\server\openerp\addons\base_calendar\base_calendar.py", line 1703, in get
  File "C:\Program Files\OpenERP 6.1-1\server\openerp\addons\base\ir\ir_values.py", line 463, in get
  File "C:\Program Files\OpenERP 6.1-1\server\openerp\addons\base\ir\ir_values.py", line 420, in _map_legacy_model_list
  File "C:\Program Files\OpenERP 6.1-1\server\openerp\addons\base\ir\ir_values.py", line 462, in do_get
  File "C:\Program Files\OpenERP 6.1-1\server\openerp\addons\base\ir\ir_values.py", line 390, in get_actions
ValueError: invalid literal for int() with base 10: 'False'