I'm wondering if anyone else has experienced a similar problem.
 
I have my mouse and keyboard connected to my sig rig via a Kensington 7 port powered USB hub (K33366US). These two devices, plus any others I have connected to the hub, work as they should. If at any time my computer goes sleep, it will wake up as it should. This is true for all modes (S1, S3, and S1 & S3).  However, when I go to shut down the computer, Windows will shut down, but the motherboard will not power off (fans still running, etc.). Also, the motherboard will show the code "FF". I have to hold down the power button to turn it off.
 
At one point, among the many, many power on/power off cycles required to find the culprit, my BIOS actually reset to the defaults on their own. Hated that. 
 
The problem does not happen if the computer never goes to sleep from the time I first turn on the computer. In that case, I am able to achieve a complete shut down and power off. Also, the problem does not occur if I remove the hub from the equation. Additionally, I have not been able to duplicate the problem with the hub on my laptop and other desktop; and I have not tried out another hub yet.
 
Kensington claims that it is a compatibility issue. I'm curious as to whether it is indeed a compatibility issue, or if it is motherboard/BIOS related.
 
I'd also appreciate any recommendations on a good powered hub that is successfully being used on the same motherboard.
 

Thanks for the suggestion. That hub seems pretty popular. I prefer a powered one, though, for when I max out the hub with all my toys. The hub's also on a 16 ft extension.

ATL FTW!! 

Oh, really? That's good. The description on Newegg doesn't mention an AC adapter. I did, however, see it mentioned on Amazon, along with some pictures.  I may just shell out another $30 and give it a try.
 

Hmm,  will your original hub function (for mouse and kbd at least) without having its power brick connected?  If you can run it w/out external power, does  your shutdown problem still happen.
 
I've had issues with some hardware of my own design in combo with some comps where power bleeding back into the system confuses the reset logic.  In my case, the comps wouldn't power up properly.  Just ran fans and sat there.
 
I don't have a fix, just curious,
Z.

I just tried a scenario where my USB hub was connected to the computer, but without any devices attached to the hub. My keyboard and mouse were attached to the USB ports on the front of my case. The problem did NOT occur. I was able able to achieve a complete shut down and power off.
 
I still need to use the hub with my keyboard and mouse, though. Any more thoughts?