There seems to be an error in clean_dvi.py in the windows version of Lyx 2.0 RC1. When trying to produce a dvi output (ctrl-D, dvipdfm or ps2pdf) Lyx gives an error (see the atached screenshot). Replacing clean_dvi.py with the one from Lyx 1.6.9 solved the problem.
You're right. I'll fix that.Joost