I just finished fixing this very problem. My gf's laptop (i'm on it right now) started to have blinking LED's after 30 mins of counter-strike 1.6, and the system would shut down after blinking at me for a couple mins. Mobmeter was telling me the cpu idled at 46-47. This indicated to me right away that something was off (kinda funny how I knew something was wrong yet I continued to use the lappie. Laziness people. Let this be a lesson to all) See, i put some artic silver on my cpu, and I distinctly remember it idling at 41. So I unscrewed the CPU portion of the laptop on the bottom.
If you look closely, theres 2 fans blowing across holes in the copper heatpipe. Upon closer inspection, I found a huge layer of dust and hair (my gf has long ass hair that gets everywhere), which was blocking the fans from blowing air across the heatpipe and out the laptop. So I removed all that gunk,blah blah then fired it up. Mobmeter is now tellling me I'm at 41 C, right where it should be.
I noticed that after awhile, the fans never turned off when the dust was clogging the heatpipe. Now, the fans turn off once in awhile when the proc hits 40 C. Surprising to me when the fans stopped just right now because I haven't heard silience from this thing in awhile. Sweet sound of silence..
Sorry for making this post so long, but yeah, just try cleaning the dust from the heatpipe kids, and everything should be ok.
oh, and by the way, if your fn +F10 is not working, it's because u also have to update the keyboard bios, not only the mobo bios. E-mail Sager. Hope this helps, kids. DOn't give up on your 8790, its a beast when its dust free, and well maintained. peace.