[MPICH] mpich2 "Internal MPI error!"

[sage weil]

Hi,

I'm getting fatal "Internal MPI error!" and am not really sure where to 
start tracking it down.  I don't get any core files, and the error 
message(s) aren't especially helpful:

1: aborting job:
1: Fatal error in MPI_Isend: Internal MPI error!, error stack:
1: MPI_Isend(142): MPI_Isend(buf=0x19c83e98, count=4, MPI_CHAR, dest=16,
tag=0, MPI_COMM_WORLD, request=0xa4088c0) failed
1: (unknown)(): Internal MPI error!

Are there any usual suspects I should check for, or is there some sort of 
debug mode I can enable to get more information?

The app isn't doing much of anything very tricky... it's doing almost 
entirely all Probe's, Isend's, Test's, and Recv's.  I'm not sure where to 
start...

Any suggestions would be most appreciated!

thanks-
sage