exceptions with ISB set to 001 (0x40 00 00)

we have a mcp565 and configured the RCW to set ISB to 001.
i think that the exception table should still be at 0xfff0 0000 (with 
MSR[IP] = 1). however during an exception the debugger stops there but 
does not execute the ba instruction.
in the old configuration (ISB = 0) the ba was executed an i could set a 
breakpoint in our exception handler.

has anybody experience in using an ISB not equal to 0?
is there something to know about exceptionhandling in that case?

thanks