I’m getting the exact same message regarding the duplicate column. Same column. I was running 1.6.2 successfully until I tried to update. Then I got as far as from 1.6.2 to 1.6.4.
I’ve re-installed and wiped and renamed and wiped and re-installed and now I can’t even get to my control panel, because it’s not recognizing my password. I tried to reset the password, but that was a bad idea because I can’t get into the system at all.
Mod Edit: Split from http://ellislab.com/forums/viewthread/107907/