Can't log out, restart or shut down in leopard

Hi, I'm running a 2 quad-core intel xeon mac pro with 10.5.8 and I recently did a security update and did a system restore on the windows xp side recently. But now when I try to restart sometimes the toolbar disappears and then it just sits, after a minute it says "Can't logout because finder failed to quit." It does the same if I try to shut down or logout. It goes to sleep just fine and seems to function fine.

When I hard shut down (hold power button and shut off power) when I turn it back on it goes briefly to a grey screen then shows a ghosted image of my desktop with 10 or so grey bars in the center of the screen that all turn white in succession then it goes right back to the desk top so I can't even run in safe mode or use the instal disk to fix it!

When I run Disk Utility it says:

Invalid volume file count
Invalid directory count
The volume Macintosh HD needs to be repaired.
Error: Filesystem verify or repair failed.

I repair disk partitions and nothing seems to help! I'm completely stuck! Please Help!

I had a somewhat similar problem with my MacBook Air about 6 months ago. I was getting the same error message about the HD needing to be repaired. After much testing, I had to take it in to an Apple store, where it was determined that my HD was failing and needed to be replaced. I don't know if that is the same problem you have, but you might want to check with an Apple authorized repair shop.