.NET 4.0 - CultureNotFoundException

I had a similar issue with the CultureName "UserCache". To resolve this I deleted all the folders from in here:

C:\Windows\Microsoft.NET\Framework\v4.0.30319\Temporary ASP.NET Files

For other people that have this problem, this is usually an exception that is ignored.

Go to the Debug menu -> Exceptions... and ensure that you have everything unchecked for the Exception list.