What format did you shoot on? If you shot DV25 and are capturing via FW then you can only capture at DV25. If you try and capture using DVCPro50 the computer will look for a DVCPro50 deck (which it obviously won’t find ’cause you are using DV25). Also, you mentioned using CD audio. On import did you change the sample rate of the audio from 44.1k to 48k?
I can guarantee you that the problem is not because you are using FW400. FW400 and DV were pretty much made to go together and I regularly capture DVCProHD via FW400 and have no problems and that’s 4x the data of DV25.
-A