fix on trunk and 0.4.3.maintenance

i couldn't test it yet, but replacing the line
code:
filename.settext(modelelement.getname().replace(" ", "_"));

by
code:
filename.settext(modelelement.getname().replaceall("\w+", "");

in exportdialog.java, line 124, should do the job of safely encoding the meeting name to a valid file name.