WordPress MU

I have latest 1.3 version of WordPress MU site
http://mynation.net
it was working fine till yesterday;
users also created new blogs
Eg: http://mynation.net/abio
http://mynation.net/voice

main site is static site; so i wanted to creat a sub blog as http://mynation.net/blog from my admin login
after creation it asked me to said blog with ADMIN login and and i posted some articles there also and logged out.

now i wanted to go into my main site to admin section,but it was taking me to http://mynation.net/blog/wp-admin
instead http://mynation.net/wp-admin.

but when on front page of the site it was showing admin logged in.
when you try to type http://mynation.net/wp-admin.
it says
"You do not have permission to access this page."

how to get back admin panel
i tried from phpmyadmin too to creat one user or grant admin rights to other users; nothing works.

any experts on this issue

I found out where is the BUG;

When you creat a sub blog when you logged in as admin; it will clear wp_sitemeta table of database;

under this table

site_admins coloumn should be like this,
a:1:{i:0;s:5:"admin";}

when its like
a:1:{i:0;s:5:"";}
admin is unable to go in to ADMIN panel; but on site it shows like he logged in.