Ah, yes...for some reason direct rendering crashes with an assertion on newer Intel drivers (since 2.1.x I think).
You'll want to use indirect rendering (which should be accelerated, assuming you have AIGLX turned on—if you're using the desktop effects, you definitely do):
$ cd (wherever your planeshift folder is)
$ export LIBGL_ALWAYS_INDIRECT=1
$ ./psclient
See if that helps. If it is, you'll want to put the export LIBGL_ALWAYS_INDIRECT=1 line in your .bash_profile or in the "psclient" script itself.
Good luck!
--Kayden