The following folder needs Read & Write access:
Macintosh HD:Users:(Your User Name):Library:Application Support:Adobe:Adobe Illustrator CS5
You can change this access by selecting "Get Info" on this folder, then adjust the Sharing & Permissions options so everyone can Read & Write.
NOTE: This addresses the startup profiles only; crashing on quit is a separate issue.
and as BOB said post the issue on Illustrator forums