GDB caching question

[Yadav, Vikas]

When I set $fp or $pc varibles in gdb for i386, it sometime does not work. Does anyone else have done 
something like this. In my case if I do a backgrace following by modification to $fp and $pc to change my stack, it does not work. However If I don't do a "backtrace" first, it works. I suspect some kind of caching of register value is cause of this behaviour.

Any insight here ?

-Vikas