Comment 149 for bug 296167

That error may just indicate a generic xmousepos error, for example I get a very similar message with an invalid param to xmousepos.

davey@cylon:$ xmousepos --help
X Error of failed request: BadWindow (invalid Window parameter)
  Major opcode of failed request: 38 (X_QueryPointer)
  Resource id in failed request: 0xa
  Serial number of failed request: 7
  Current serial number in output stream: 7

this might be interesting a perhaps we could use it to have a cron job doing an xmousepos every second and autofixing the pointer if an error is reported, although I'm happy enough with the mousefix script attached to a hotkey.