First of all let me say that FreeRTOS is a Great project! Problem: I was doing some USB stuff on a AT91SAM7S64 when I was getting Data Aborts (dabtvec), Prefech Aborts (pabtvec) and other unexpected results and eventual crashes (hangups). Cause: Lack of task stack space.  I was setting the task stacks to 100 (in SAM7 it is 100×4 bytes).  My estimations of local variable calculations were correct BUT the GOTCHA was the functional depth.  I totally ignored the stack usage when functions are called.  As you get deeper it uses more stack to store your parameters etc. Solution: Increased the stack size.  Its working like a charm since then! Cheers

Thanks for the feedback.