Im running 3.0 kernel (on one media director) as well because of particular nVidia card.
lsusb returns 'Bus 001 Device 004: ID 2040:4901 Hauppauge' for my hdpvr (which is different than yours.... I have an earlier 1212)
as long as the hdpvr module is loaded, and a valid /dev/video device is created, mythtv should see the card when selecting the Card Type as 'H.264 encoder card (HDPVR)'
Let me know how the upgrade to 12.04 works, I am at 10.04.