Did you try to eliminate system-wide problems?It's a good idea before and after major system updates, to run a safe boot (reboot and hold down the shift key during system startup), then Disk Utility to repair permissions.
Here's more info on those steps
Mac OS X 10.2, 10.3: How to start in Safe Mode Repairing Permissions File System Check and Repair (fsck) more details what "Safe Boot" is doing