HTTP Status 500 in IE but not in FF

System

Hi all,

Recently we upgraded to Version 6.1.0.0.0 Build 56030 and for some reason after we try to login to OD admin it gives us HTTP Status 500 in IE but not in Firefox. In Firefox everything works fine but in IE only page that loads is login page and that's it. Does anyone have any ideas please? Tried basics like restarting admin gui and server but no go.

Thank you in advance.

I have to add that we tested this from many different locations so it's not from one computer. There are about 70 or more users that are in different countries etc. that can't use IE for OD Admin.