I would boot from your install DVD and run both Disk Repair and Repair Permissions.
Start from your Mac OS X Install disc: Insert the installation disc, then restart the computer while holding the C key.
When your computer finishes starting up from the disc, choose Disk Utility from the Installer menu. (In Mac OS X 10.4 or later, you must select your language first.)
Important: Do not click Continue in the first screen of the Installer. If you do, you must restart from the disc again to access Disk Utility.
Click the First Aid tab.
Click the disclosure triangle to the left of the hard drive icon to display the names of your hard disk volumes and partitions.
Select your Mac OS X volume.
Click Repair. Disk Utility checks and repairs the disk.
Mac OS X (10.6.4) <--- your profile
If that is correct, updating your system software may stop the blue screen issue.
Click the Apple menu (top left in your screen) then click: Software Update ...
If you system software is up to date ...