Check your apt-get logs to see what went wrong, then try apt-get again, and one more time, and if the problem persists, report it to the apt-get people :)

When folks (repository admins ... ) package stuff for binary packagers (apt-get, ppm, whatever), sometimes they make mistakes and conflicting something gets packaged with conflicting something or something file doesn't get overwritten with the correct new one ....

the packages are supposed to catch this kind of error but they don't some times