Christoph,
Welcome to The PainterFactory!
Rob,
The stuck-on-the-screen Enhanced Brush Ghost thing happens to me, too, now and then.
It seems to be related to other screen refresh problems, though that's only an intuition-based guess. Screen refresh problems occur, for me, when I've been working in Painter X (now Painter X.1) for too long (an hour or more) and especially when I have other resource-intensive programs running at the same time.
When following my own advice (see Keeping Painter 6 Through Painter X.1 Running Smoothly - Updated February 6, 2008, by Jinny Brown ) these things, and other performance problems, don't seem to happen so often.
Cheers!
Jin