OK, after a long struggle, I convinced a site owner to upgrade their site from 2.3.3 to the latest version 2.7x
However, while the site is functioning after bringing in the data to the new dev. version of their site (we're doing it there, modifying the data from the main domain to a subdomain in anticipation of a re-design)...
I cannot get to the wp-admin portion of the site -- I get the following error
At first, it was saying that there was an issue with the pluggable.php file in the includes... I commented out those lines and now am left with just the above appearing rather than a login screen or anything else.