I'll update that ticket to see if I can get a pair of expert eyes to take a look.

Behavior:
UltraEdit 3.0.0.11 crashes when reorganizing [dragging from one location to another] the text editor tabs.

Output:
Gdk-ERROR **: The program 'uex' received an X Window System error.
This probably reflects a bug in the program.
The error was 'BadWindow (invalid Window parameter)'.
  (Details: serial 264782 error_code 3 request_code 18 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.)
Trace/breakpoint trap

Relevant information:
1) I cannot reproduce the behavior using Gnome as the window manager
2) I cannot reproduce the error if I run with the --sync command line option
3) I can *only* reproduce the crash when  'Enable display compositing' option on the Compositor tab of Window Manager Tweaks is enabled.

It's because of #3 that I thought this may be a good place to post. I can provide all the usual nitty-gritty details about my environment, ldd, and full gdb output if anyone is interested but what I would appreciate initially is just some informed advice such as 'there is no way this is a xfce problem' or 'yeah, this could be a xfce problem'.

I don't want to overwhelm with info right off the bat but here are the first few stack frames from gdb:
(gdb) bt
#0 0x00000031cae4d313 in g_logv () from /lib64/libglib-2.0.so.0
#1 0x00000031cae4d6a2 in g_log () from /lib64/libglib-2.0.so.0
#2 0x00000031d4e6ab2b in ?? () from /usr/lib64/libgdk-x11-2.0.so.0
#3 0x00000031cd24810f in _XError () from /usr/lib64/libX11.so.6
#4 0x00000031cd244f91 in ?? () from /usr/lib64/libX11.so.6
#5 0x00000031cd244fd5 in ?? () from /usr/lib64/libX11.so.6
#6 0x00000031cd245de0 in _XReply () from /usr/lib64/libX11.so.6
#7 0x00000031cd2415a3 in XSync () from /usr/lib64/libX11.so.6
#8 0x0000000000ea5589 in wxTopLevelWindowGTK::SetTransparent(unsigned char) ()
#9 0x0000000001078270 in wxAuiManager::HideHint() ()
#10 0x0000000001081441 in wxAuiManager::DrawHintRect(wxWindow*, wxPoint const&, wxPoint const&) ()

Thanks in advance,
jb