Macbook OS10.5.7 won't shut down.

My white Macbook OS 10.5.7 won't shut down. Happens intermitently. Begins to shut down but then stalls. The desktop clears but the doc remains. Tried to ask on the mac forum but I need to pay because my warranty ran out (thanks apple!)

I ran disk utility's with the install disk in and fixed a problem but this didn't help shut down. Also tried taking the battery out and resetting SMP but not sure if I did it right. Thanks for any help.

MacBook won't shut down

Wondering about my MacBook, almost every time I try to shut it down, it stalls and I have to hold the power button to force it to shut down. Everything looks normal, then it stalls on just the desktop background I have (without any icons, doc, or hard drive icon in the top right), it's only the background with a round cursor spinning in about the center bottom of the screen. Very strange I'm worried about what the problem is, I think it started when I left the computer on a few times without being plugged in with the power cord (like falling asleep to music).

I run Mac OS X v. 10.5.8
Processor: 2GHz Intel Core 2 Duo
Memory: 2 GB 667 MHz DDR2 SDRAM

I have the Disk Utility, MacJanitor, DiskWarrior, don't know if I need to reinstall the software or upgrade from 10.5.8, don't live near a Genius bar so would be great to get any answers, thanks!