We have one server that shows this error:

Server Error in '/' Application.

Culture is not supported.
Parameter name: name
en-001 is an invalid culture identifier.

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. 

It works on the other 2 servers, and we use the same database. What could it be? I havent specified the culture anywhere, and i have not specified any templates, so everything is standard!