I am having a problem installing Dropbox in Ubuntu 12.04
Files in subdirectories of /var are locked preventing the completion of installation
There could be one of two issues with this.
If you do have a broken APT and you are sure you have exhausted any other option, try removing the lock and doing a reconfigure by doing:
This should remove the lock and reconfigure dpkg, so you should be able to install again. be careful not to shut down your PC while installing something via APT again.