Saving images gets error "Image type not supported: application/octet-stream"

[mdmcginn]

Binary package hint: gthumb

Description: Ubuntu karmic (development branch)
Release: 9.10
AMD 64
gthumb is 3:2.10.11-1ubuntu1

I'm unable to save any images using gthumb. Whether I open an existing image or try to save a new cropped screenshot, I get the same error message "Image type not supported: application/octet-stream"
IT works fine when I use Gimp to save the image.

ProblemType: Bug
Architecture: amd64
Date: Thu Oct 8 22:59:29 2009
DistroRelease: Ubuntu 9.10
ExecutablePath: /usr/bin/gthumb
Package: gthumb 3:2.10.11-1ubuntu1
ProcEnviron:
 LANG=en_US.UTF-8
 SHELL=/bin/bash
ProcVersionSignature: Ubuntu 2.6.31-12.41-generic
SourcePackage: gthumb
Uname: Linux 2.6.31-12-generic x86_64