MBP freezes, but I can still move the cursor on trackpad? Please help.

[logicstudiouser]

Running 2011 Macbook Pro on 10.6.8

I have a random issue that is continuously happening and I have been trying for weeks to fix it.
At random times in the day (mostly when I am quitting applications, but not always), the computer will freeze, everything comes to a stop, the time freezes, the applications freeze, the whole operating system freezes but I can still move the cursor with the trackpad (I Just can't click anything). If music is playing when the freeze happens, it still continues to play.
The ONLY way out of the freeze state is to do a forced shut down by holding down the power button. This is happening very frequently and it is quite annoying.
Has anyone heard of an issue like this?

Here is what I have done to try and fix the situation:
1. Launched Disk utility, verified and repaired disk, verified and repair disk permissions.
2. SMC reset
3. PRAM reset
4. Defrag using Disk Genius
5. Erased, re-installed operating system and imported my time machine backup via. migration assistant

I tried to find a way to track what is going on when it happens by going into the 'console' application in utilities when I restart, but I can't find activity at the exact time (minutes and seconds) the system freezes.

Any tips?

 

[JTToft]

Could be this: http://www.apple.com/support/macbookpro-videoissues/

Which screen size do you have?

 

[logicstudiouser]

Could be this: http://www.apple.com/support/macbookpro-videoissues/

Which screen size do you have?

17" model. I did get the logic board replaced just before my extended warranty expired in December. Looks like I may need to go that route again.