Admin blank page 500 error

[avansant]

I updated a site from 2.5.27 to .28 and the upgrade just went to a blank page instead of installing successfully. I only got the site back up by installing a clean copy of 2.5.7, exporting the content from the old DB, importing it back into the new db, then exporting it from there, deleting the old content table and replacing it with that one.

No, I didn't make a back up before upgrading. I'm an idiot.

Anyway, now everything is back to normal except the Administrator comes up blank. If I enable error reporting through .htaccess, it comes up 500 error.

I've tried totally replacing the administrator directory with a clean copy of both 2.5.27 and 2.5.28.
I've double checked all permissions on that directory
I've switched from bluestork to hathor through phpmyadmin

Nothing gives me a clue what is wrong. Are there any other things I can try? I won't have time to upgrade to 3x until next month.

[avansant]

Little update. I found that if I swap out the current Libraries directory with a 2.5.27 verison, the admin login will appear, but once I log in, blank page/500 error again. I think all the files on the servers were turned into 2.5.28 but some database upgrade didn't happen. But without an admin, I don't know how to "fix" it, and I'm not even sure 2.5 had a "fix" option?

[avansant]

And now for no reason that I can figure out I just see the Joomla Logo in the admin. and part of the code if I view code.