NOTE: JEFF SHOULD CHECK THIS!
I found that orterun was not tracking the index number of the app_contexts it was creating. Hence, the app_context->idx field was always sitting at zero. This index is used by the mapper to decide which app_context to use for each process - thus, with the value of each index being zero, the mapper only used the first app_context that was created. All others were ignored.
Not sure when this might have gotten changed. Could be it was a problem that always existed, but didn't get exposed until something else was changed.
Anyway, it seems to work now - could stand further testing.
This commit was SVN r9389.
2a18ebd9e1