I was one third through the single player missions in UO when the bug hit me. For some reason, at the start of the British campaign, where you're a tail gunner in a B-17, the game quits at a certain point. When I checked, there was a patch available on the net (a whopping 320mb patch) which I downloaded and installed on the off-chance that it would solve the problem. Once installed though, the game refused to recognise previously saved games ... so I've had to start all over again ... back in the snowy woods of the Ardennes ... sigh.
(knowing how these people do things, this is probably only an issue with the mac version)