I haven't messed with IGMP proxy at all, but it seems to come pre-enabled on the Rev. I. From what little I know about it, I think you would want it enabled unless you're experiencing DLNA issues like you said. Still, I suppose it couldn't hurt to turn it off and see if it makes a difference with the chronic rebooting issue. We've tried just about everything else.
As for strange log entries, oh yeah, I've got TONS. Most are cache entry/mac errors that seem to come every few minutes. This router has no shortage of weird stuff going on.