I've recently built a Media PC using Vista Home Premium, with the intention of using Vista's Media Centre to replace my PVR (attempts with Ubuntu and MythTV failed horribly). I've gone for a low power, light-weight option and have used the following hardware:

* Intel Dual Core Atom 1.6GHz Mini-ITX D945GCLF2 Motherboard
* Corsair 2GB DDR2 667MHz/PC2-5400 Memory Non-ECC Unbuffered CL5
* Western Digital 320GB 2.5" Hard Drive Scorpio Black SATAII 7200rpm 16MB Cache
* Slimline DVD/CDROM
* Happauge WinTV Nova 500 Tuner
* picoPSU-90 DC-DC ATX power supply (90 Watt) and 80W AC Universal Adapter

Everything works like a dream, the CPU is plenty good enough for standard def stuff but i'm having one major problem. I can get Vista and Media Centre to sleep (S3, confirmed in BIOS) but there's nothing on this earth that I can do to wake it up again. A keyboard tap or pressing the power button will spark things in to life, i.e. the drives power-up, the fans power-up, but i'm left with a blank screen and a humming box but no Media Centre - ever!

I have to unplug the mains power and do a cold boot to get back to the OS, where everything works perfectly. There are no errors in the event log and no clues as to why this problem is happening. I have a support call open with Intel but they're just giving me the "have you tried turning it off and on" type responses.

Does anyone else have experience in solving this particular problem? I've tried stripping the PC down to a bare minimum, i.e. remove CDROM drive, remove WinTV card and switched off on-board devices (sound card, LAN, etc) with a view to reducing it's power consumption (Intel suggested the PSU might be insufficient) and it didn't make any difference. I've tried the latest, and previous two, BIOS versions, all to no avail. I've also tried booting from an Ubuntu Live CD and trying Ubuntu's Sleep functionality and that produces exactly the same result.

If no one can suggest a solution, could anyone recommend a tool/approach for performing some diagnostics?! I've run SiSoft's Sandra Benchmark but, to be honest, I don't really know what i'm looking for.

(Sorry if i've put this in the wrong group and sorry it's a bit of an essay!!)