BSOD Starting, Playing, Internet Explorer And In Idle. Error 116?

A couple of months ago, I bought a new graphics card: a Nvidia 560GTX (Gigabyte GV-NV56GOC) and a new PSU (Corsair CX500 V2 Builder Series, 500 W) to run it and after 3 weeks the PC began to fail with the 116 error.At the begining it crashed only at Windows 7 blue starting screen (after the loading screen with win logo and a progress bar). It happened once every 4 or 5 days.After a month it was almost imposible to run unless starting in "FailSafe Mode" and began to crash in the desktop in idle. I tested it with another drivers, clean installs, changing cabes, etc... and nothing worked, only with another graphics card (an old nvidia 220GT wich came with the PC) and worked properly so I decided so send the card in RMA.

A couple of days ago the seller sent me an email saying that they couldn't find any issue with the 560GTX and they sent the card to Gigabyte to further testing (I wil have to wait 20-30 days to have more info). Yesterday my PC with the old card (the 220GT) began to fail while playing Skyrim with a grey screen and a strange buzz in the speakers. After 2 seconds it restarts saying that there was an system error bccode 116. Today it has crashed 4 times in 5 hours while playing (same as yesterday), "youtubbing" or (I think, but not sure than) in idle with a white screen and a strange buzz in the speakers, but not starting like with the 560GTX.

I had to change my HDD a month ago too so I tested in 2 diferent HDDs, drivers are OK and I guess that the PSU is enough for the new card and more than enough with the old one. I also ran sfc.exe /scannow witho no problems.I'm running Windows Home Premium x64 (Service Pack 1) OEM, reinstalled one or 2 months ago. I will attach minidump files with errors of both cards.