I have the same problem :
backTrack system information disabled due to load higher than 4.0
after this message i type 'Start X' and boot the graphic interface ... once the booting is complete all the USB are disabled and i can't install the OS on the HD ...
I m using a MacBook Pro :
Model Name: MacBook Pro
Model Identifier: MacBookPro9,2
Processor Name: Intel Core i5
Processor Speed: 2.5 GHz
I ll try today to install the BTR R2 And upgrade at 3 ... Maybe is easiest than fix this problem ..