Seems like the package is messed up.
I tried just using Stable, then just Testing, then just unstable and finally a combination of All 3 it always gives a bunch of needs so and so but it is uninstallable errors. The errors change slightly depending on which repo you use but no matter what it refuses to install using APT/Synaptic.
You might try using Gnucash instead. Or try installing it from source: