"One thing to try is to rename the existing dpkg directory, then see if Synaptic will automatically create a new one
" is not true in my case. i fix my problem, and the solution is perfectly true in this type of problem.
here we gooooooooo.
we are at root
1. mv /var/lib/dpkg/status __/var/lib/dpkg/status_bak
2. cp /var/backups/dpkg.status.<any latest number>.gz __/var/lib/dpkg/
3. gunzip -d /var/lib/dpkg/dpkg.status.<any latest number>.gz
4. mv /var/lib/dpkg/dpkg.status.<the number in third step> __/var/lib/dpkg/status
5. apt-get update
I hope next time you please address the whole problem, but not the first sentence only.