[gembud] gemplt bombs in wrf-ems 3.0 script

I've successfully run wrf-ems and I used the "ems_post --gempak" option with
the automatic script to make gif images turned on.  Everything goes well,
but no images are produced.  I checked the log and found one of these

[GDCNTR -3]  Fatal error initializing GEMPLT.
Error in message send = 22
itype, ichan, nwords,0,27492352,3
[GEMPLT -101]  NOPROC - Nonexistent executable.

for every gempak program the script ran.  I can produce a gif if I run a
gempak program on the terminal, so it's not really a non-existent
executable.  I start up a virtual display with Xvfb before processing so
that the scripts can create the gifs within gempak.  I've cleared message
queues and all that jazz.  Is there something about the virtual display
that's causing gemplt to fail?