Hei, although this thread is a bit old...

...i think i got to the gist of this.

Some packages in Extras are packaged with a dependency against a specific version of python2.5-qt4-.... . Namely this is version 4.7.4-maemo0.

However, Extras-Testing has python2.5-qt4-...... at version 4.7.5-maemo4.

Now, if for some reason you have ever pulled in those newer packages from Extras-Testing, apt won't like downgrading them. When packages that request the specific (lower) version do their dep check, apt see's a newer version is already installed and rejects the dependency.

What you can do:
1) use apt-get to remove the newer packages (4.7.5-maemo4). This will also remove any packages depending on them, note them somewhere.
2) disable Extras-Testing
3) use apt-get to re-install the dependent packages noted under (1). Note that you can only do this for packages in Extras, not Extras-Testing (as it's not active yet, and we don't want it active, yet)
4) (optional) re-activate Extras-Testing and install the remaining packages, if any. However, make sure this doesn't upgrade your python2.5-qt4-.... packages again.

To summarize, the issue occurs because some packages are packaged in a bad way (requiring a specific version of a dependency is generally not a good idea). The package maintainers should be contacted to fix this.