I'm sorry, I tried to run apport, but as I'm trying with 3.0 kernel it's unable to send the report. It just added an unity-2d tag (I don't know why?).
Anyway, with 3.0.0-0300rc7-generic #201107120911 SMP Tue Jul 12 10:15:32 UTC 2011 i686 i686 i386 GNU/Linux I'm able to do vertical scroll again.
$ cat /proc/bus/input/devices
I: Bus=0011 Vendor=0002 Product=0005 Version=0000
N: Name="ImPS/2 Generic Wheel Mouse"
H: Handlers=mouse2 event7
B: KEY=70000 0 0 0 0 0 0 0 0