I would suggest you install your graphic drivers and also try the Gnome version of Backtrack.
I have Backtrack 5 R3 KDE64 and it keeps crashing at the same spot and puts lines across the screen. I have never had problems running backtrack on this machine before so I thought maybe the disk that it is on was scratched up so I re-downloaded it and burned it onto another disk and it is still doing the same thing.
This is what it is doing: (will post vimeo link when it finally finishes uploading -.-)
I tried safe mode too and it shows a bunch of lines of code and then it freezes.
Could it be a driver acting up? The only thing that is different on my computer from when I last used it is the new video card I put in.
Any help is greatly appreciated.
Windows 7 Ultimate 64-bit
Phenom II x4 B55 3.5GHz
GTX 560 Ti