Constant Hard Boots

I posted this in the macbook section but it I am looking for an answer that involves my harddrive, so perhaps.....


OK I hope someone can help me with this and while I looked to see if it was already asked and answered I could not find. I have been using grease monkey, which is a script reader, I guess, in order to stream tv shows and movies from the internet off of this site using FireFox...and since then every once in awhile, and it only happens while I am watching something...a line will go down my screen darkening it and then a error messages comes up. It says in 3 other languages that I need to reboot my computer and basically to do a hard boot. Normally I will restart it and it will boot back up fine but once I got the file and blinking question mark. I didnt know what it was from, I do now, and I did another hard boot and got it again, I got nervous but luckily the 3rd time it booted back up and has been working fine, accept from when it locks up and tells me I need to do a hard boot. My concern is, is this causing damage to my computer? doing all of these hard boots and perhaps someone knows why this is happening? I have a macbook pro using mac os x 10.5.8