I shoot and capture in HD. Have had a client hand me a mini dv with what looks to be DV 16:9 footage (except it shows as 4:3) on my camcorders screen. If I try and capture it, Vegas capture just locks up. Tried recording it across to another camera and also a third camera. Same on all three.

I am not sure what it was recorded with.

Any ideas?

If you're using Vegas Pro 8, odds are that you have the capture utility set to HDV exclusively.
If you can't switch to the DV capture utility in the Video tab of the Preferences screen, it's at C:\Program Files\Sony\Vegas Pro 8.0\vidcap60.exe