Asus 7950 3GB DirectCUII Shutdown Issues

So I bought a used video card locally a few days ago. I always test used hardware before buying so I plugged the card in my PC and fired up Furmark for like 1 minute and a half and everything was fine so I paid the guy and he left.

After more testing I realized that the card was behaving really weird. My PC would completely shutdown after putting load on the video card or loose video signal. I thought ok, it might be a power supply issue so I tried the card in 2 other systems with quality 600 watts + PSUs and same thing happened in every PCs. I contacted the guy but he said the card was working perfectly fine for him and that I must have done something wrong or missing something in the BIOS eh. If he reimburses me, I'd be surprised as hell..

Anyways, the card works fine in windows (2d mode), web browsing and stuff. Could it be an overheat issue ? My CPU is 100% fine. I just find it weird that my whole PC shuts down if the video card overheats. Is it a built-in safety measure? Should I remove the stock cooler and reapply fresh thermal paste ?

edit: I think I found the problem: http://www.behardware.com/news/12153/asus-hd-7950-directcu-ii-fault-report.html

Yeah that's not good.
Also a lot of miners are selling off their 79xx cards. While most are ok after a few months of mining some are less ok

What type of temps are you seeing from the card?

I made some custom ghetto washers and it looks like I fixed my problem (inspired by this post here: http://www.overclock.net/t/1349821/asus-hd-7950-direct-cu-ii-overheating-faulty-cooler/30. I haven't replaced the TIM (I might do it at some point later) but so far so good.
Contact between the GPU core and heatsink was off just a bit. It's a very common issue with that card it seems like. I ran Furmark for over 10 minutes and no crash, same with AIDA GPU stress test

idle at around 37C at 10% fan speed full load at around 55-60C (50% fan speed, manual)