Version 1.7 was given two instances of the same file (created a group) and, coincidentally, had the same (private) IP address. How this might happen is:
1) Two people who use the same NAT range and ended up having the same fourth octant, or
2) One person who has the same file in more than one shared folder.
Anyway, when the group was highlighted and the download button clicked, LimeWire popped up the "Report this to the developers" window. It happened every time. When the group was expanded, I selected one of the instances and had no further problems.