breakpoints yes, step no

I have an embedded system with a PPC8541 using remote debugging across the serial port. I am using Fedora Core 6 on my host along with DDD 3.3.11 and Linux 2.6.17.11 on the PPC8541 target.
 
I can stop the kernel boot with 'kgdbwait' on the command line, startup ddd/gdb and set a breakpoint on do_fork which triggers reliably.
 
>From there, I can delete that breakpoint, set a breakpoint further along in do_fork or continue using ddd to a location further along, but I cannot execute 'step'.
 
When I execute a cont from either the gdb window or the ddd window, I do see the message:
 
"Can't send signals to this remote system. SIGILL not sent.
 
This problem occurs with or without ddd running the inferior debugger, so I suspect it is a gdb/target issue and not necessarily a ddd issue.
 
Mostly, I am trying to understand what is going on.
 
Charles