When I digitize from a JVC deck (SR-DMV70, although the same problem occured with the 600U) to 8.2.2 (G4 1.25 GHz; 1 MB memory; 10.3.9 OS) only about 16 minutes are digitized when I get a loss of sync error and the digitizing stops. I am using the firewire in/outputs, machine control is Media 100 DV and DV deck is Generic, footage was acquired with Canon XL 1.
Starting with the easy stuff first, does the error coincide with a break in the recording on the tape? Unlike the analogue inputs, digitising always stops when there's a break point in a DV recording when the media is coming in via firewire.
Is the error happening at the same point on the tape? Have you looked at the tape via a video monitor to see if there's a visual break-up at that point?