Adding the first three torrents is fine; they find seeds and start downloading. Quite quickly I might add.
If I add a 4th torrent, the speeds drop to zero and transmission locks up. I get a spinning beach ball and I have to force quite transmission. If I delete the 4th torrent, then kill transmission, it starts up just fine and the three torrents go back to happy downloading.
It doesn't matter which torrent is the 4th, I've tried different ones.
Any ideas?
MBP running Snow Leopard, fully updated.