Unable to get to my App Store on my IMac after ITunes 10.5.1

I have an IPad, IPhone, MacBook and at work I have an IMac. I use only one apple_id and I´m Norwegian, living in Norway.

When i go to App Store or ITunes on my IMac I´m only getting the US store, not the Norwegian store and are thus not able to buy anything. I don´t have that problem on my other devices, using the same apple_id.

The problem occured after the latest ITunes upgrade (10.5.1 (42)). I have also upgraded on my MacBook. I have two colleagues sitting next to me with the same ITunes version and I can log in there with my apple_id and get the proper store. They get the same problem as me if they log into my IMac.

I guess there must be a setting somewhere telling itunes that my IMacislocated in USA, but I can´t find any. Regional settings are Norway. I have tried signing out/in, booting etc., nothing helps. Anyone with the same issue?