Insomniac PowerBook Problem

Hey everyone,

First post here...nice to meet everyone! Anyway, I'm at my wit's end. I've been having problems with my PowerBook sleeping for the last 2 months and I'm out of ideas. I'm relatively new to Macs, perhaps you guys have some suggestions. Here's the deal:

My PowerBook will often not sleep when I close the lid or select Sleep from the Apple menu. The display will freeze or turn off, but the hard drive will continue to spin and for all intents and purposes the computer is "on." It won't respond to any input and I must manually turn it off. The sleep indicator light will never come on. This isn't every time though. At times it will go a day or two with no issues and then the problem will crop up 3 times the next day.

Here's what I've done:
I've reset the PMU twice, I've zapped PRAM, and after no other software fixes worked, I wrote 0's to the drive and did a clean install of OS X to rule out any software problems. A bit extreme perhaps but I'm getting desperate. The only apps I run that I could see causing a software problem are Quicksilver, Adium, Desktop Manager and a Cisco VPN client for use on campus. However, I seem to have the problem whether these apps are running or not. I've talked to Apple Support and they've suggested I do the stuff I've already done. If anyone had any suggestions I would be much appreciative! I can give anyone more details if they like...

 

Additional info

For what its worth, I'm running 10.3.8, its a 15" 1.5GHz PowerBook G4.

 

Negative on the Bluetooth device. I've experienced the problem before 10.3.8. I got the PB in June and had no problem with sleeping until January. All of the apps I'm running now I was running well before that point. I'm just not sure whether or not to think its software or hardware. Apple Support was less than enthusiastic about me sending it in because the problem can't always be readily replicated. I'm not too keen on sending it away for a week if they aren't going to be able to reproduce the problem and then send it back not fixed.

 

I actually just have one 512 MB SO-DIMM stick that it was shipped with. I didn't add any third-party RAM or anything, which was actually one of the first things that Apple asked me about. I've run a few hardware diagnostic tools, all of which claimed everything was cool. If this is a software problem tho, I'm baffled...