The m2v is an mpeg2 file rendered from Vegas. I think the m2ts is straight from the camera, and I can't take that into PPro CS3 either. I think CS4 is needed?
M2t is a Mpeg2 File! MTS is a AVCHD file straight out of the camera.
It can be open in Vegas Pro 8 / Edius 4.5 / Premiere Pro CS4 and CS3(with MPEG Pro Plugin).