reboot on resume

I upgraded my dekstop HTPC to w8 from w7 yesterday and am having issues with sleep mode. it worked perfectly in 7, but in 8 when I press the power button on my mce remote it puts the computer to sleep no problem, but when it wakes it up it simply reboots. it sounds like it's coming back on fine, then it reboots and never shows anything on the screen (until post) and no dump files. the biggest conundrum and the fact that I don't think it's a driver or other kind of problem is that wake-on-lan works fine and wakes the computer with no issues whatsoever.
he only indication I get that there was a problem is from event viewer that talks about losing power. "Event 41, Kernel power. The system has rebooted without cleanly shutting down first. This error could be caused if the system stopped responding, crashed, or lost power unexpectedly."

Store bought or self built? How did you upgrade; describe? Clean install or reuse existing partition structure? Details please.

it's an asus m2nsli board with 2 gigs of ram and a quad core. nvidia gt220. w8 over top of w7. I am using mce tool and plex, but have tried it with them both disabled with no change. I can only assume it's an ehome problem since WOL works perfectly.

I've isolated it to the tv tuner card (avermedia a188c). not sure that there's any fix though.