This message pops up due to the missing text.gxt. If you miss one of the three needed files in the MPACK (scr.scm, mpack.dat, text.gxt), you can't open the MPACK.
I can't say why it crashes when you used text.gxt. Do you have any (conflicting) cleo mods? Perhaps also the CLEO3/CLEO4 problem, like Nitesh said.