Thats quite odd as I have upgrading a few installs etc that I have done the last couple days to 5.1 and get no such issue. I use FireFox as my default browser. Try though letting it sit there and complete.
The upgrade itself also is quite small so it isnt a big one. If you continue to have issues you might want to use phpmyadmin to add the necessary fields.
Also on your install since its kinda huge and your using VB3 try at line 2052 after this