WordPress MU

My colleague logged in as an administrator to edit the blog and changes the Defaul User Status from Administrator to Subsriber. As a result we cannot login to Admin interface anymore. Can you please suggest a way to reset the Admin status? thanks in advance

Were you using the Site Admin account?

You should be able to log in using the Site Admin account, go to Site Admin -> Blogs, pick the blog you can't log into now, and click on Edit. Then reset the users in the right-hand panel to whatever permissions they should have.

The blog was set up at http://vive.matosyan.com/ and we used to login from http://vive.matosyan.com/wp-login.php. Now when I try to login at this site using our admin and password it does not do anything. Before that my colleague changed the status of admin to Subscriber.

Please note that the site used to have only one user - admin. can i somehow reset the status via PHP files through FTP?

See this thread.
http://mu.wordpress.org/forums/topic/13444?replies=10

Also, I know with version 2.8.5.x if you're logged in as admin and try to change your role from administrator to author it won't let you.

"can i somehow reset the status via PHP files through FTP? "

no. the values are stored in the database.