AFAIK it's always been like that. People have complained about it before. Overall size of the interface will remain after changing, as will any new columns you add. But column dimensions may or may not change back between openings. If you originally had LW 4.9 or earlier, what you could do is start from scratch by deleting both LW prefs if there are 2 sets.
Fixes for Limewire I'm wondering if you it may be an issue with having the earlier LW prefs folder. But on the other hand, if I set my chat column to be narrow, it tends to stay that way next time I open LW.