XPS 420 No audio device after sleep mode (Vista SP2)

I've seen a lot of posts on this, but have not encountered one that contains a sure-fire resolution to this issue. Outside of doing a full OS reinstall, I need to know what I can do to get the on-board audio detected again. I've updated the BIOS, attempted a driver install and it's just not happening.

Granted, this might be a good excuse to finally scrap everything and install 7, but I'd like to try and get this working before then. Any assistance would be greatly appreciater.