Strange error message (INTERNAL EMACS BUG)

In XEmacs 21.0 "20 minutes to Nikko" [Lucid] (sparc-sun-solaris2.5.1) of Fri Apr 9 1999 on brabham configured using `configure --prefix=/app_share/xemacs/21.0.67 --with-jpeg=no' When I switch my virtual window manager window away from a virtual window in which I have a Windows terminal server running back to the window in which xemacs is, I get the message you can see below. I have no idea what is special about the Windows terminal server window, except perhaps that it causes colormap flashing on my xterm (if that means anything) wheras none of the other virtual windows do. Also, when I come back from the Windows window, the "I beam" cursor in xemacs is too fat. It changes back if I take it off the xemacs frame and back on again. The error message below occurs even if focus is not given back to xemacs - the message happens as soon as the virtual window is mapped back. It doesn't happen every time, either, of course :-) I'm using fvwm2 for window manager. Wierd, huh? Martin. Recent keystrokes: b u g RET C-s x e m a c s RET ESC x r e p o r t - e m a c s - b u g RET S t r a n g e SPC e r r o r SPC m e s s a g e RET C-x 1 C-l SPC C-a C-h l C-x k RET C-x o C-x k RET C-h a b u s BS g RET ESC x r e p o r t SPC C-g C-l ESC x r e p o r t - e m TAB RET Recent messages (most recent first): unrecognized selection-conversion type: nil, #<INTERNAL EMACS BUG (opaque, size=4) 0x783640> unrecognized selection-conversion type: nil, #<INTERNAL EMACS BUG (opaque, size=4) 0x783640> Quit Loading view-less...done Loading view-less... unrecognized selection-conversion type: nil, #<INTERNAL EMACS BUG (opaque, size=4) 0x783640> Loading emacsbug...done Loading emacsbug... Quit Quit