How can I recover a gnumeric file?

[Pete Crite <hypocrite lawyer com>]

Hello,

I'm trying to open a gnumeric file that had worked in the past for me.
Opening the file via `xdg-open` fails silently. Opening the file with
`gnumeric /path/to/file.gnumeric` freezes the command line and fails
silently. Launching Gnumeric first, then opening the file from within
the program causes the "Reading file…" progress bar to freeze while loading.

I'm happy to try and find the cause of this bug, but I have some
important files that I need to extract from the gnumeric file urgently.
Is there a way to recover the contents of the file? I tried opening with
a plain-text editor, but the contents were garbled. Similarly,
Libreoffice Calc didn't know about this format.

Cheers,
Pete.

Kubuntu 13.04
Gnumeric 1.12.1