bdi2000 + mpc8560ads, very early breakpoints

I'm running a bdi2000 (with mpc85xx-gdb f/w 1.03) with a mpc8560ads 
target, and I'm trying to set breakpoints early on in linux startup (in 
the head_e500.S code that sets up tlb's).   I'm setting the breakpoints 
from within the bdi telnet interface.

I can:
--succesfully hit a breakpoint set up to any instruction <= the address 
of the first 'tlbwe'.
--single step (with the bdi "TI" command) past that 'tlbwe' as far as 
I've cared to try

I cannot:
--hit a breakpoint once the first 'tlbwe' has executed.  If I attempt to 
do so, linux startup doesn't proceed, I lose further communication with 
the target and the BDI claims "COP Freeze" and I have to reset the target.

Btw, the 'tlbwe' in question marks invalid the first tlb1 entry setup by 
u-boot, which pointed at flash address space.  Code is running out of 
ram at this point.

I'm probably missing something very basic here.  Any ideas?

Thanks,
Kylo