Updating a live machine.

Hello all. If I update my machine using yast and a locel DVD from 9.0 to 9.1, should this work? The update/upgrade bombed out on only one rpm, filesystem. Bit of a difficult one there as I'm fairly sure my install would need filesystem :-) Qusetion is, should I have booted from the DVD and done an upgrade? If so, why did yast let me try? Dave.