I thought I'd share my experiences on how I got 10.6.3 working on my G31M-ES2L board. I had a number of issues with the first upgrade and went back and installed from scratch.

First of all a full system restore from a local Time Machine doesn't work. I never managed to get the boot partition to work after this. A restore of user accounts, and everything else does work though.

I had a working system through following this guide all the way to 10.6.2. USB worked fine, I had the initial black screen on first boot until the screen saver kicked in and I never, ever got sleep to work

I wanted to upgrade to 10.6.3, I followed the instructions here, removed the sleepenabler.kext, upgraded to 10.6.3 and then applied the new upgraded sleepenabler.kext. Blue screen, mmm.... lets downgrade using Time machine back to 10.6.2, rats, either it doesn't restore or screws the boot partition <sigh>, do proper install from USB key.

Full install from USB key, chose to restore user and applications from the Time Machine backup and, blow me down with a feather, it works.

Took sleepenabler out, upgraded to 10.6.3, installed sleepenabler and this time it worked. No idea why.

However my external powered USB hub would connect and disconnect every five seconds or so. I noticed this as I have an iMic connected to the hub to power my speakers as I don't use the internal audio. This was originally because my external speakers didn't have a volume control and the output from the motherboard was too loud. I have since changed the speakers but left the iMic in as it was a zero maintenance item and I didn't have to worry about sound kexts as it was external.

I could see errors in the console so looked further into the problem. There were definite USB disconnects. A trawl round the internet produced this site

http://tonymacx86.blogspot.com/2010/...63-update.html

I could see there were some USB issues and various fixes. Since I didn't understand DSDT I thought I'd simply download the
"Non-Vanilla USB Solution - For Non-DSDT Users with No USB " fix.

http://www.tonymacx86.com/Public/10....yInstaller.zip

I ran this and rebooted. My USB issues had gone, no disconnects, no problems so far.

As an aside my black screen on initial boot has also gone. I have not yet fixed the sleep issue but lets cross that bridge later

hope this helps somebody.