Why does Macbook Pro have gray "curtain"and msg to shut down when playing video online?

Question

Hi,
I have a MacBook Pro running Snow Leopard v 10.6.8 and have put on all the security updates.
I bought this machine just days after the newest MBP's were released with Lion because I wanted to stay with Snow Leopard
From the very beginning I would have occasional "gray screens" with a message that I'd encounterd a problem and needed to shut down.  It always occured while I was watching a streaming video online (Flash?) but it didn't always happen.  I updated my Flash plugin and that seemed to help.  I use both Safari and FireFox and both are now updated to the latest versions.
I had also noticed via iCleanMemory that my memory availability was very low .....I always have many tabs open in my browsers and have backup software that backs up to online storage running and when I watched a video, it dropped to almost 0 and everything ran slow.  I had 4 GB Ram.
So, I ordered new ram and put that in and now have 8 GB.  Machine runs fast. Love it....except it keeps giving me that veil of gray and the message to shut down.  It happens several times a day now and while usually in conjunction with watching a video clip, it's not always the case.  But I have lots of available memory.  That wasn't the issue.
I found an Apple Support paper relative to needing a video update on some mid 2010 MBP's and downloaded it.  It won't install and says it won't run on my system so that didn't help.
I'm at my wits' end trying to keep this thing running.  Everytime I have to shut it down it means a minimum of 8 min...sometimes more.....before it will restart.  If I try to restart sooner than that, it begins to boot and then just has lines and lines of numbers and code running across it....and often continuous beeping sounds and I have to hold the button down to shut it off again.  If I wait long enough, it does boot back up and sometimes runs fine as long as I'm not watching video clips, a streaming tv show or clicking on a lot of links in web pages.
I don't believe it has shut down when I was doing anything that wasn't web related....i.e. on a browser. And, when I was running with only 4 gb ram, it rarely shut down, just ran very, very slowly.  Now with 8 gb ram it is speedy but doesn't seem to want to keep working!
Anyone have any ideas what I should try next?
Thanks
Paula

Answer 1

Hi Allan,
Thanks for your reply.
I have been closing iCleanMemory but the shut down (kernel panic) was still happening.  Not sure how to go about uninstalling it as it's one that runs at start-up and dragging it to the trash might not get rid of it completely.  I"ll find it's web site and see if they have any info.
Haven't checked your web link yet (it's late and gotta get to bed) but will do so tomorrow.
I also run Backblaze and DropBox that begin at startup and are constantly updating in the background, iStatMenus and Sharpshooter. 
The kernel panics were happening....tho much less frequently.....before i put iClean Memory on.  If I remember right, I installed it just because I had those periodic shut downs and wondered if it was a lack of memory.  Because I then saw that memory was very low all the time, I decided I must need to put more memory in.  And that seems to have made the issue worse while also making the machine work faster for the time it is running.
Now, I've been working on here for a couple of hours and had no problem at all......but I haven't asked it to play any kind of video.  Before I quit for the night, I'll try to watch the last one I tried that caused it to shut down and see if it does it again.
I do appreciate your help as I have just enough knowledge about these things to be dangerous.
Paula