Hi, my Vista media centre has been pretty much OK, unmolested and updated only occasionally and carefully. But recently I've been having a pretty bad standby problem..

If I power up and start live tv, everything is OK.  Press standby (S3 state) and it stands by ok.  Press power up-> live tv, everything is OK again.  But the second time I try to enter standby, Vista appears to ignore the first 'standby' button push on the remote.  If I push the button a second time, the box goes into 'away mode' (as it normally does before standby) but then it never enters standby. It seems to stay in away mode with the display off but everything else on.  After this, nothing will get it to leave 'away mode'.  Even pressing and holding the power button for 5 secs doesn't work - it appears to power down, but a subsequent power up will leave it in the same weird 'away mode' with power on but the display off and nothing happening (no disc activity either).  The only fix is to turn it off at the wall.

I've tried the MCE Standby Tool, I've tried uninstalling everything apart from the OS, and I've tried updating every driver/BIOS/windows update etc. etc. to no avail, and I can't find much help around the web.  Motherboard, CPU, chipset and disc temperatures are OK.  Different RAM doesn't help.

Please, does anyone have any ideas I can try?
Thanks,
-Mat