Version:           4.0.0 (using KDE 4.0.0)
Installed from:    Gentoo Packages
Compiler:          GCC 4.2.2 x86_64 
OS:                Linux

When I run xchat under kwin4 it crashes very frequently. The crashes happen when new windows such as chat rooms open. The same application works with out problems when running in kde3.5. The error I get is:

The program 'xchat' received an X Window System error.
This probably reflects a bug in the program.
The error was 'BadMatch (invalid parameter attributes)'.
  (Details: serial 140528 error_code 8 request_code 2 minor_code 0)
  (Note to programmers: normally, X errors are reported asynchronously;
   that is, you will receive the error a while after causing it.
   To debug your program, run it with the --sync command line
   option to change this behavior. You can then get a meaningful
   backtrace from your debugger if you break on the gdk_x_error() function.)