Thanks to Philippe for all the useful tips, particularly MacJanitor which seems like a very useful little application. Unfortunately none of these fixed the problem. I've had a look at what's going on in the activity monitor. Limewire gradually uses up all the available memory until there is about 5M left, at which point everything slows to a crawl. The Virtual Memory size and real memory used by Limewire keep creeping up and the processor and disc activity meters hit the endstops. Looks like a memory leak to me, but whether it's a bug in Limewire or OSX 10.3.9 I've no idea. I'm pretty sure that the problem only started with the update to LW4.10 though. If only I hadn't clicked on that download button. Anyone know how I can go back to an earlier version of Limewire?

Deano