So that makes my current specs (to see my power needs):
q6600 @ 2.8ghz (from 2.4)
560 ti @ 860mhz (from 822)
2x7200 hdd (1 sata, 1 ide)
6gb DDR2 RAM (2x2gb, 2x1gb)
a few system fans
and all that is powered by my 550W mushkin PSU (~2 yrs old).
My symptoms are:
1) When the computer goes to sleep and I resume it, (whether by usb or by power button) everything seems to resume fine except for the video card. All the fans spin up (including ones on the video card) and it gives me a little status is good beep but I get no video. Only way to get video is to hit the restart button and hope I get back into windows... see symptom # 2.
2) About 3/4 of the time when I power up the machine I get 1 long beep followed by 2 short beeps and I get no video again. Looking at: http://www.computerhope.com/beep.htm I see under the AWARD Bios (I have these -- Abit ip35-e) my beep code seems to mean: "Indicates a video error has occurred and the BIOS cannot initialize the video screen to display any additional information".
3) My overclocks seem pretty weak to me and they will seem stable but then fail when playing bf3. Example: I started my q6600 (g0 stepping) adventure straight off the bat at 3.0ghz because I have an aftermarket cooler and sure enough with the right voltage it booted into windows and I was able to run prime95 for a solid hour at ~55C before I declared it stable. Now at 3.0ghz, when I load bf3 I will get to the end of the "loading" screen, right before you join the game... and the OS will crash (no BSOD, just blank, black screen).
EDIT: Also maybe I should mention that speedfan reads my +12V as 6.76V (I've heard software can be unreliable, and besides... would windows even boot that low?) but in the actual BIOS it reads like 11.79V.
TLDR: Basically, is my PSU underpowered? Could it be the reason for these problems?
The first thing I would do is set the complete system to stock frequencies, then see what happens.
Well when this first started happening the first thing I did was reset the CMOS (so back to stock) and it kept happening for about 4-5 restarts... I thought the video card had died and was ready to RMA until I put an old GPU back in and it worked fine. Then when I put the 560 ti in it randomly decided to boot up.
I know this sounds like a simple case of logic that if the old card works and the new one doesn't its the card using too much power, but I've run bf3 with this new card at these current overclock levels before and it ran perfectly... even GPU benchmarks like furmark. I can't imagine how it could pull more power by simply starting the system than by gaming or running a benchmark specifically meant to get the GPU as hot as possible.
Just to be complete, I checked my PSU and its 28A like you said.
For a system using a single GeForce GTX 560 Ti graphics card NVIDIA specifies a minimum of a 500 Watt or greater power supply that has a combined +12 Volt continuous current rating of 30 Amps or greater and that has at least two 6-pin PCI Express supplementary power connectors.
Your Mushkin Enhanced 550 Watt (550200), with its combined +12 Volt continuous current rating of 28 Amps, doesn't meet the minimum requirements.
The excessive ripple on the +12V rail is destroying the capacitors on your motherboard and graphics card.
JonnyGURU.com only gave the Mushkin Enhanced 550 Watt power supply a 6.5 rating.