I have only one of my four Ubuntu (all on 11.04) equipped machines running Ubuntuzilla, and until Firefox was updated to 5.0, I never really noticed a problem but the U-zilla machine does not update beyond 3.5.5. Trying to update or reinstall with apt-get I get an error telling me that the package has been diverted by a third-party installer;
"/usr/bin/firefox has been diverted by a third party package which didn't specify
a package name to dpkg-divert. This is usually as a result of installing unsupported
packages from Ubuntuzilla.
***This is a BUG. Please report this bug to the vendor of the third party package you installed***"
Even after removing Ubuntuzilla (which no longer seems necessary) I still get the same problem.

So. How do I cure this and get my system to update Firefox properly?