Screen flicker and freeze

I have a 2007 MBP (A1226) and so far have had very little problems with it until recently. What happens is my screen will begin flickering or flashing on and off rapidly and then finially freeze after about a minute or two of doing this. After this I have to do a hard restart only to have my computer freeze at the startup screen. I can usually get it to boot up fine if I hard restart it one more time. I honestly have very limited idea as to what this could be, graphics card is my only guess (Nvidia 8600M).

Some background on my MBP: I dropped it a month or so back and ever since the hard drive doesn't make the same noise when it wakes or boots up but I'm not really sure how this could be HD related and It has been fine until just yesterday. I installed extra RAM about 2 years ago so I doubt it could be related to this since I've gone this long with no problems.

Any ideas or suggestions to help me diagnose? Thanks.

 

just fyi for anyone else experiencing this problem...I believe it has something to do with the recent 10.6.6 update apple released and the flash plugin. Not sure if there is a fix but hopefully apple will respond ot this quickly. Anyway here something I dug up on this:

http://discussions.apple.com/thread.jspa?threadID=2729291&tstart=0