Win7 doesn't want to generate any thumbnails

That is good news. You might want to try looking in Event Viewer to see if you can find anything. There is also the Reliability Monitor that might offer a clue.

I'm thinking your anti-malware program had something to do with it or some type of scan, maybe a toolbar.
When was the last time you checked for malware?

Did you install or uninstall anything before you noticed "It suddenly happened"?

Read, and follow the tutorial.
Open event viewer as shown under Here's How.
When it opens look under Windows Logs\Applications.

The reliability Monitor isn't as technical, you may like that better.
Read, follow the tutorial to open.
Then follow step #4, to see any of the problems for a more detailed report.
You may find warface there.

As for malware I would need to know what program(s) you have installed to help you with that.

Please don't be bashful about information, the more you can relate to us, the better we can help you. Even details you may think as unimportant can be of great significance.

gameInst.exe is related to Company of Heroes (COH), and the Exception code: 0xc0000005 relates to a possible memory problem you should run memtest+86 to rule out memory problems, and Faulting process id: 0x1fc0 relates to the problem you had with installing COH.

Sometimes, depending on a users machine setup, game installation, and or running the game can cause problems. You may have to remove all games, steam, origins if you run any EA games, anything to do with them and start the installation process over.

But, you should make sure your machine is stable first by following this tutorial: Troubleshooting Steps for Windows 7, and then reinstalling the games and their helpers.

I can foresee your problems will get out of hand quickly and even though you haven't gotten any BSOD's yet, you would get better help if you posted in BSOD Help and Support - Windows 7 Help Forums If you do, make sure you run the tool and post the results, and you can link back to this thread for background.

And remember:

Please don't be bashful about information, the more you can relate to us, the better we can help you. Even details you may think as unimportant can be of great significance.

Just so we are clear, the tool I mentioned is the diagnostic tool on the BSOD forum, and when you run memtest:

Part 2: Testing

3. Let it run until at least 7 passes are completed, or errors are found (whichever comes first). The longer you run it, the better.

Source at: RAM - Test with Memtest86+

Some users will run memtest overnight because it can take so long.

If you are going to create a thread over at the BSOD forum post the tool and memtest results.
Post a link here so I know where your thread is.