I was trying to enable a language pack in MS CRM 4.0 and the following error appears "Error Occured"
I checked the application folder in the event viewer and I found the following error:
MUI Provisioning failed. Error: Cannot insert duplicate key row in object 'dbo.LocalizedLabel' with unique index 'ndx_LocalizedLabel_ForSingleSelect'.
The statement has been terminated.
to solve this error install this hotfix from microsoft: