This tip was given to me by a co-worker at Colorado State University where I work.

The problem was Firefox was starting very slowly, froze often, and often required the user to end the process.

After a bit of Googling he landed upon this link: http://kb.mozillazine.org/Locked_or_damaged_places.sqlite

Turns out his places.sql file was over 200MB, after running this fix everything seemed back to normal.