This happened one time before, and I can't remember how I fixed it. I think the solution was to reinstall gnome while saving your settings. Here's the problem:

Normal boot up with no errors.
User logs in and nothing loads.
After 20-30 seconds a portion of a grey box appears in the top left hand corner.
When you mouse-over the box, the cursor turns to a type tool cursor.

My guess is this is an error message that is not being placed in the right quadrant on the screen. Reboot will not resolve this issue. Ubuntu's recovery "Fix Broken Packages" and "Fix X Server" does not resolve the issue. I know this is not an update issue because my laptop runs the same OS configuration and it's only happened on my desktop.

Thanks!