This is in Fedora 19 with current Gthumb 3.2.4. Likewise reproducible in Ubuntu 12.04 with Gthumb 3.1.2 (from a PPA).
Steps to reproduce:
1. Open foo.png
2. Select File > Save As
3. Name the file foo2.png, select Save
4. In the Options dialog, select Cancel
5. Back in the Save As dialog, select Save again
The Options dialog now only has Title and the Cancel and Save buttons, no actual options to choose from.
What I expect to happen:
The Options dialog to have options just like at step #4.
The bug crops up when saving the file as JPEG as well, I just used PNG as an example. It also happens regardless of whether a file is chosen for overwriting or not. After the bug is triggered, subsequent attempts to Cancel and re-enter the Options dialog always bring it up empty, until the Save Dialog is exited (either by Canceling or by going ahead with the Save).