USD,Linear time code Sync

[PeterD]

Recently have had to do several sessions using 40 Protool tracks or more, synced up to an analog 24 track machine.The 24 track is freewheeling,that is..it's not being driven by house sync or any other external synchronizer.I'm feeding 30fps timecode from track 24 into the timecode input of the USD which appears to be receiving properly(it's display is showing the advancing TC numbers)The USD settings are as follows..LTC for clock ref and LTC for positional ref.I was under the impression that the USD could accurately chase to within a 1/2 frame or so purely from incoming Timecode in this manner?Now I realise the correct method is to have both the 24 track and the USD slaved to a master sync device but in this particular studio this is not possible.My problem is this..ProTools chases fine for a short while and then jumps out of chase and just sits therewith the "waiting for Sync" message flashing.I open up the Peripheral dialog and reselect the USD and Printer port and everything will be fine for a while until it happens again..sometimes even this doesn't help and I have to close and reopen the session to get it to recognise and lock back up.All the timecode settings are correct as far as frame rate,non drop etc.Is this a problem with the computer being too slow (a stock 9600,too many tracks,or incorrect settings)I managed to finish the sessions but
only after much frustrating resets..thanks in advance... PD