I'm having a similar but worse problem. I'm also using Limewire Basic, and upgraded to Panther about a month ago.

However, since yesterday, everytime I open Limewire, it gets to the 'Limewire Pro' nag box, and as soon as I hit 'Later', my entire machine freezes. My. Entire. Machine.

I've repaired my permissions, installed the Limewire upgrade, and its still exactly the same.