Odd. I've yet to move from Knoppix to another user, but running as Knoppix, snapping open Konsole and typing gvim works fine. If, on the other hand, I'm (so to speak) graphically Knoppix, su to root and type gvim, it opens as well! WOW! I've never seen that before: certainly SuSE always used to pop up the errors you're getting. I'm running a knx-hdinstall on KNOPPIX_V3.2-2003-06-06-EN.iso.

Does look very much like a permissions issue.......