Does your server use PHP5? If so, un-comment the first two lines in the htaccess file (in the root directory) :
Action php5-cgi /cgi-bin/php5-cgi
AddHandler php5-cgi .php
That fixed problems I was having. I’m not sure if it will fix yours.
You can also clear the cache folder under var:
/var/cache/(a bunch of cache files) delete what’s in the cache folder. This has helped some people.
ALSO, I realized that my install had failed because of the MySQL permissions I had granted for magento. I was using read/write defaults, which caused errors. I temporarily granted full access for the upgrade, which solved those issues.
To better assist you, it would be helpful to know exactly what you’re experiencing. Any error messages? What’s going on? Remember, magento is complex and thus users will experience complex problems. Don’t make the job of people that offer to help you more challenging by not providing equally complex/detailed information about the issues you’re having. We need a better description than “I can’t login to my Admin page! “. What had you done prior to the problem? What have you done since?
So just let us know what’s going on. No detail insignificant.