Restarting on Shutdown/Waking from Sleep after Upgrade

So yeah idk if this is the quite the right sub but it's custom computer and I started getting weird behavior when I added a 2tb HGST HDD to my gaming rig so I might as well start here.

Tuesday I added the drive, set it up, played some games, and set about downloading my steam library overnight. Wednesday after work I noticed that my computer was now restarting on shutdown and instantly waking up as soon as it entered sleep.

As far as I've seen, it seems stable during normal use once it's on, but is pretty defiant about staying on short of flipping the psu switch.

After disabling the obvious wake timers/WOL prompts I'm still having the problem. I've also since updated windows (7sp1, 64bit btw) and manually installed any missing drivers I could find. Weirdly enough the problem hasn't shown up when I unplug my external powered usb hub from the computer (also fairly new, though oddly, installed two days prior) and I'm wondering if it might have something to do w/ the ports or the cable. At this point I'm wondering what steps I can take to try to identify the exact conflict and if anyone else has had similar problems that could shed some light onto this.

Thanks