Do you get an error message or will IE just not open? This is a guess, but
I wonder if you could be short on RAM? If you have plenty of RAM, then
perhaps IE needs more memory assigned. Navigate to the IE icon in the
Finder, select it (click once) and Get Info (Command>i). Switch to the
Memory pane and increase IE's Preferred memory by 5000K. Leave the Minimum
memory setting alone.