Ok--I took apart my wheels and did a complete inspection, but didn't find anything. Now the only thing that makes sense to me is what DebW is saying about a mismatch between the rim and the tire bead. I took it to LBS today and had it checked out. He said everything looked fine to him too, but if I have further problems, to come back and he'll contact the manufacturer. He also suggested inflating partially, moving tire around a bit, and then filling it up. He's also not all that impressed with super light tubes, so I guess I'll switch to something else (possibly Conti's--thanks cusepack).
Thanks again to everyone for your help on this!