Today I got an error on a web application after upgrading it from .Net 2.0 and Visual Studio 2005 to .Net 3.5. The project uses Telerik radcontrol, a few releases old version. After upgrading, every page that uses the radcontrol DatePicker failed to load, and the dreaded "Yellow screen of death" was shown instead.

It wasen't my code that failed, it was the radcontrols own prerender-event that threw the exception. Since I don't have the source code for this control and due to the fact that the fault only appaired on one test server without Visual Studio installed, it was hard to debug. Luckily a colleague had experienced a similair problem some weeks ago, and I remembered that changing the locale settings helped him (He is swedish, and used a swedish locale in an otherwise homogenic norwegian development team).

I logged in to the server and tried to change the system locale of the admin user. No help.
I tried to change the user running the application pool from NETWORK SERVICE to the admin I logged in as. Suddenly everything worked.

I did however want to run the process as NETWORK SERVICE and not administrator or have to make another account just for this reason. Therefore I wanted to change the network services locale settings, but since this is a user you can't log in as, this seemed hard.

Luckily I found this blog post: IIS6: Changing the Locale ID when Regional Settings Won't Work
I followed the description to change the settings. For some reason this didn't quite work. Probably due to a typo. I tried to export the regedit settings for HKEY_USERS\S-1-5-20 and just manually change the sShortDate, from the English setting and to norwegian settings. Now everything is working again!