Do you have any thermal paste lying around that you can use, that is nonconductice/noncapacitive? Noctua Nh-1, artic Mx-4 or Ek exotherm?

If so, it is really fast and easy to change the thermal paste as well as clean out the fins of the heat sink that may have dust build up.

I will wait for your response

Also another question, where exactly would I apply the thermal paste on the GTX 660 SC?
 

Scarlet-Tech
You will be applying it to the core of the GPU, where every ounce of hateful heat is being generated.  This is the first step in checking to make sure the paste isn't dried out.  Once you let me know what kind you have, we can get you a good walkthrough to make sure you are able to do it with great ease.  Actually, LinusTechTips just did a video, so I will link it to you.
 

 
Things to remember:
 
1. Take your time:  It takes about a week or two for an RMA, spending an hour replacing the thermal paste is not a bad thing.
 
2. Slowly rotate the heatsink once it is free to verify it isn't stuck on anything like another screw.
 
3. Disconnect the fan before you pull the shroud away all excited that it came off :-) lol
 
4. Lint free cloth or coffee filters are your friend.
 
5. Once you are finished, reconnect the fans lol.. (I have forgotten them before, so I have to say it.) 
 
 

I cleaned out the dust surrounding the graphics card and now on the idle temps it runs 49 celsius is that normal?

Eh, it's running a bit on the high end at idle temperatures, but that's fine. The GTX 660 can run at a maximum of 97 degrees Celcius, so you're fine. Also, if you're not comfortable with taking apart the card and replacing the thermal paste, you should look around your case and see if there are any extra cables hanging around that is obstructing airflow, or clean out some fan filters. It also might be the ambient temperature in your room, but 49 degrees is an ALRIGHT temperature at idle. Just remember, if your card gets too hot, it'll throttle its own performance to keep the GPU at a safe temperature, so there is a small risk that you'll burn out your card, unless you're overclocking. Just consider the various factors that could also be affecting your GPU temperature, such as cable management, fan filters, dust build-up, etc.
 
Good luck with your 660, enjoy!

If it's starting to lag and freeze/go black randomly, I would think that something is wrong with your card. Maybe there wasn't a good contact between the heat pipes/heat sinks with the VRAM modules or the chip itself is just not getting enough cooling. The fan on your card is spinning, correct? If not, is the 6-pin power connector plugged in all the way, is the fan header plugged all the way in on the card's PCB? You can also try to take apart your card and replace the thermal paste, but if you're not comfortable with doing that, I would suppose that your card is faulty. I'm fairly certain that the GTX 660 chipset won't thermal throttle at 80C, and thermal throttling doesn't result in freezes or black screens, or at least I don't think so. I would suggest you contact EVGA's 24/7 technical support, if you don't get good enough answers, or just straight out start an RMA. Sorry to hear that, but I think that an RMA is your best option. At least call tech support first. Cheers!