Have you tried increasing the baud rate to 250k? That did the trick for communication errors on my sanguinololu at least.
Perhaps you can try out pronsole.py or printcore.py directly to narrow down the problem. Also, if you run pronterface.py from the console, you will see more error messages than what pops up in the GUI.
I'm no linux veteran, but my printers run fine from my xubuntu box, so perhaps it could be a serial driver problem?
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-Nudel
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