Here's the answer I got from the guy at SteadyHand:
Rick,

It does run on Vista 64.
It handles some HDV -- there are many formats.
No it doesn't open m2t files. Only AVI in AVI out.

:(

Erik.... I too get that message in Vegas 8.1, so dropped back to 8.0c, where I experience the problems described above.

i dont have time to play w/this yet. is it true that it won't handle m2t? i need this on HD 1440x1080i .m2t footages =(.

can som1 confirm?

I think that's it.

If you mean Deshaker, yes it will work with m2t files so long as you are using the script from within Vegas Pro.

so u can use deshaker on .m2t only if u have 32-bit OS, otherwise people w/Vista64 (like me) won't be able to use it unless it's .avi yeah?

Actually, the script in Vegas is rendering out to AVI even in the 32-bit version so the same procedure should work in 64-bit.

I use Vista 64. The OS is not an issue with Deshaker, but VDub does not natively recognize m2t files in standalone mode. You have to use the Deshaker script.