Do you still have your old version of LimeWire kicking around anywhere? If not, you could download it from:
http://www.limewire.com/download/1.4/LimeWireWin.exe
It would be a tremendous help if you could check whether or not this was a problem with 1.4 as well, as we are unable to duplicate that issue internally. (don't worry, I won't hold it against you if that's too much to ask =)).
Also, I assume that you are using LimeWire 1.6b beta? If not, you might want to give it a try at:
http://www.limewire.com/beta/1.6b/win/LimeWireWin.exe
Thanks for all of your help.