I get this problem on all of my systems at one time or another, and there doesn't seem to be any rhyme or reason as to when or why it happens. Sometimes I go for weeks without a problem, other times I've seen it come up two or three times in about half an hour. I finally gave up trying to make heads or tails of it, and just have my system reconnect & rejoin channels automatically.

Various systems running Window 98SE, Windows ME, Windows XP SP2, & Xandros