Version 1.3.9.1
on Hardy Xubuntu.

Built with ..
./configure --prefix=/usr
make
sudo make install

Here are 3 instances of output when xfce4-screenshooter crashes ..

1.
The program 'xfce4-screenshooter' received an X Window System error.
This probably reflects a bug in the program.
The error was 'BadWindow (invalid Window parameter)'.
  (Details: serial 3611 error_code 3 request_code 15 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.)
2.
  (Details: serial 2868 error_code 3 request_code 15 minor_code 0)
3.
  (Details: serial 3341 error_code 3 request_code 15 minor_code 0)

(2. and 3. have the repeated info removed)

It is partially intermittent, but I could fairly regularly repeat it if I chose 'Take a screenshot of the active window' and choose to open with either GIMP or GQView.  I don't think that I ever got the crash when I chose 'Take a screenshot of desktop'.