Latest Security Update is causing headache for PPC programs in 10.6 Rosetta
Restore
Backup files off the computer (not TimeMachine) and disconnect.
If you have TM, or a option key bootable clone use that to erase and restore from.
If not, c boot off the 10.6 disk, use Disk Utility to >Repair Disk and Permissions, (do not format or erase!!) and simply re--install 10.6 from the disk.
Note: This 10.6 reinstall does not touch your files and most programs (provided you don't erase), but backup your files regardless.
Note: If Disk Repair gives a error that is not repaired, then you have to consider erasing the drive (with Zeros) and try reinstalling 10.6 fresh or replacing the drive.
Reboot and log in, update to 10.6.8, it should not include the security update at this time (second pass it might show) because it was just released and they might need to pull it. (they need to pull it)
When you reboot, make sure to reinstall any programs that installed kext files into OS X, you'll know, they won't work.
If you get gray screen, hold the shift key while booting and update your installed software so it's compatible with 10.6.8.
Note: If any of this is beyond your ability, no problem, I'm no brain surgeon neither, call in a professional before you lose your data.
Learn how to clone here
http://www.bombich.com/get_ready_for_lion.html
TM help here
http://pondini.org/OSX/Home.html
Learn how to make copies of your 10.6 disks here
http://www.walterjessen.com/make-a-bootable-backup-snow-leopard-install-disc/
Learn how to make a bootable SL USB
http://www.maciverse.com/install-os-x-snow-leopard-from-usb-flash-drive.html
Learn which programs ARE NOT compatible with Lion
http://roaringapps.com/apps:table
Long live the Snow Leopard. 🙂