Based on your extra vague description, I'm guessing you overwrote your SQL database connection settings in plog-config.php with the blank file that came out of SVN. Open up plog-config and put in your database settings manually, upload it, and try upgrade again..
ill wait for v3 final now, the only reason i wanted to upgrade was because i was having issues with Lightbox... though i fixed my issues and im happy now.
only other issue is centering the thumbs. but i cant wait for that :)