The problem here is that either the DVD player or the DLP set is applying video processing that creates a delay in the video signal. If the delay only appears on DVD's, then it's the DVD player's processing that's creating the sync problem. The 1050 does not have a lip sync adjustment - the center channel delay is to compensate for different distances from speakers to the listening position, so that sound from each speaker reaches the listening position at the same time. A visible sync error is going to involve anywhere from 15 to 50ms, and receivers that offer a proper audio sync delay typically offer 100ms to 200ms of delay in increments of 1ms, 5ms, or 10ms.
Unless your DVD player has an audio delay control, the only way to adjust would be to either get a new receiver or invest in an external device. There are a couple audio delay devices, but they're pricey.