I had been having a similar issue, and this is how it was resolved.

PROBLEM: Logging in as Admin produced a blank page.

SOLUTION:

Log-In as Admin (get blank page), then modify url to admin section:
(http://yoursite.com/admin.php)

Once in, turn on PHPDebug from Preferences-->System--General Settings

Save.

Then, open your site again. An error message should follow. In my particular case, the error was:

Fatal error: Call to undefined function: error_die() in /homepages/18/d128327878/htdocs/mastery/modules/uskolaxgallery/blocks/gallery.php on line 162

From this point, still in the Admin area, I went into "Blocks", deleted the faulty block that was causing the error.

All is well now.

Hope this helps any other souls that may encounter the same.

Cheers

Thanks for the head's up...

I have upgraded to 2.2.3Final and this problem no longer manifests. Interestingly PHPDebug never showed an error.

Happy now!!!!

Cheers