whenever i open kdenlive and similar video editors my computer crashes. why does this happen? is there something else i need to install? please help.

Well your description of the problem is a bit short. If you want help, we need details about which distribution, which Kdenlive and MLT versions you have, how you installed them, and please have a look at some basic tests you can do in our bugs page: http://kdenlive.org/bug-reports

its KDE - Be Free!
Platform Version 4.6.5 (4.6.5)

I just installed it yesterday. I installed it thru synaptics package manager. I simply load a movie or clip. as soon as i start to even play it in the kdenlive program it crashes and forces my computer to reboot. its not just kdenlive though I also have pitivi which is the default editor which does the same thing. everything else on ubuntu seems to be working fine. I also had a crash when i played movies in the mdeia players but fixed that with some kind of code entered in the trminal given to me in the ubuntu forums that must have been codecs or plugins i needed, but the editors still dont work and crash. I tried avidemux which works but the audio is messed when saved. this is the best information i can provide. please help. i like kdenline since it has a timeline and would like to use it just need it to stop crashing.