advc-100 skipping

I am converting old Hi-8 and some old VHS camcorder tapes to DV. I'm using a Sony Vaio with 4gb RAM, 200gb HD and Intel dual core processor. The advc-100 has been working fine most on most of the tapes but occasionally it starts skipping. I can't tell what is causing it, system or tape? It did it on one of the Hi8 tapes then about halfway through the first VHS tape it did the same thing. I've turned off and on the system and the advc-100. Including unplugging it several times. (which seemed to help the first time it happened) But this time it continueds to skip/drop frames. I tried capturing using the pass-through on my Sony DCR-HC1000 and it caused skipping too. Do some of the tapes get corrupted time code or something? Although it doesn't seem to happen in the same spots. It behaves more like the system is short on resourses but it is not. Is there anything that can be done to help like changing the DIP switch settings or something?