I haven't been able to connect either. I have the same problem as others where all I see is the LimeWire splash image and the program opens but a second later it quits.
I tried the telnet thing and I wasn't able to connect, BUT, on a whim I tried to open my 1.6 version and it's working flawlessly. Methinks there's a bug in the 18.c version. If it's any help, I'm on an AMD K-62 500MHz running Windows 2000 Professional.

-sketch