Nope. Didn't fix it. I went out for dinner, came home, and Limewire showed five red bars and the "you don't have an internet connection" dialog box. Of course, I have an always-on internet connection so this is patently ridiculous. Closing the dialog and telling it to "connect" sufficed to fix it however, without restarting the client. So maybe there's some improvement; although switching to Java 1.5.0_04 didn't stop the problem happening in the first place it may have made it easier to recover from.

(Sanity check: yes I could browse Web sites just fine both before I left and right when I got back. No, I hadn't changed anything -- in fact I wasn't physically present to have changed anything even accidentally, this time.)