Hm. I am not a Vista expert, but it does occur to me that your previous uninstall was not complete and you may have to manually clear some remaining bits. A mail to limewire support would probably advise.
Regarding the inabillity to connect, this is far more likely to be an issue with either a firewall block, or your ISP has started peer to peer blocking. There is an excellent thread concerning this elsewhere in the forum, with some possible workarounds.