I've lost heaps of blocks too. This was from machines that I know weren't on randoms because I had buffered nearly a weeks supply. 500 blocks gave 200 on dnet. One flush of about 400-500 just dissapeared? This was on a new machine that I hadn't flushed before, but had new packets from Mika's on it.
OOM
Well waddya know! The missing blocks all came back and reappeared on dnet? Hang in there, there might be nice surprises for others as well.