I am having this exact same problem. The limewire box pops up but no text appears on the bottom of it like it should then it disappears after about 2 seconds. I've tried uninstalling and re-installing and the same thing happens.

I have limewire 4.12.15 with java 6 v2, win xp sp2[all updates available as of 7/23], athlon xp5400+ with 2 gigs of ram, 200+ GB's of hd space, linksys cable modem and router. Limewire works fine on the other PC hooked up to the router.