With the latest ProspectHD build (3.4.6 Beta) Premiere CS3 crashes on me when I drag any of the Cineform 32-bit color filters (levels, balance, correcter) onto a clip (1080i CFHD 1440x1080).

I've only recently upgraded to Prospect so can't say for sure whether these filters were working for me previously. Anyone else seeing this?

Not seeing that here, those filters are working fine, and they haven't been changed in a very long time (other than the addition of Levels.) Try a re-install.