Indeed I don't know if this is a bug - it seems to have happened ever since you could resize the nicklist from the right side of the scrollbar. In versions prior to 6.0 the little <-> symbol would appear on the left side of the scrollbar closer to the channel window, whereby you could still right click and see channel popups. From mIRC 6.0 onwards it was 'changed' (intentionaly?) so the <-> symbol appears on the left hand side of the scrollbar. Tested specifically on 5.9, 5.91, 6.0, 6.1 and 6.15, XP Home.