Jason: The most likely reason is a bad font
So start by taking any fonts which are not standard to the OS (ie, fonts you downloaded, bought from a third party font foundry, etc) and move them out of the fonts folder to a temporary folder.
Try to launch AE. Does it work? If so, try adding back the fonts you removed before, one at a time, until it fails to launch again, in which case you will indentify the offending font.
Do you use a font manager? If not, I recommend you use a tool like OnyX to clean out your system font cache. Also go looking for instances of AdbeFnt.lst files. these are Adobe's own font lists and may sometimes get damaged. Deleting them will force a "deep scan" next time an Adobe program starts and rebuild the lists. Anbd of course go looking for that offensive font. In particular "free" fonts are prone to causing errors as from a technical point, they are often not well engineered.
BINGO! That did it! Thank you so so much Adolfo .. now the task of actually finding the bad font. Thank you again. Cheers!
Thanks Mylenium for that too .. I was looking into Onyx earlier .. I think I got AE running now ... Thanks!