WordPress MU

I am having trouble activating a new theme and deactivating current themes. I recently upgraded to wpmu 2.7. Can someone please help me solve this problem.
thanks

trouble activating a new theme and deactivating current themes

How 'bout describing what trouble you have? :)

Okay, I uploaded a new theme and went to the them admin page, selected yes to activate and then clicked update theme. it returns a page with two forms and a button below that says authenticate. When I select activation I get a
:Redirect Loop

Firefox has detected that the server is redirecting the request for this address in a way that will never complete.

The browser has stopped trying to retrieve the requested item. The site is redirecting the request in a way that will never complete.

* Have you disabled or blocked cookies required by this site?
* NOTE: If accepting the site's cookies does not resolve the problem, it is likely a server configuration issue and not your computer."

thanks