7 works for me, you just have to use a recent wine and
follow the tips at http://wiki.winehq.org/GoogleSketchup
If that doesn't work for you, please let me know the version
of Linux and of Wine you're using, and what graphics card you have.
You can still get 6 by going to http://www.google.com/intl/de/sketchup/download/
and selecting the language you want, I think.