'E: Internal error opening cache (1)' what the hell is this??

Yet another Ubuntu problem but there is always helping hand in the form of community.Last week,I was installing Virtualbox and I cancelled it while it was downloading required packages.After that whatever I try to install from Synaptic Package Manager I encounter a message 'E:internal error opening cache(1)'.Obviously Googled and found an answer.I have edited my /var/lib/dpkg/status file (sudo gedit /var/lib/dpkg/status) to remove the entry of half-installed Virtualbox.Magically it worked and I could install everything again.