I am facing the same issue, I run 5 copies of wow over 2 computers.... only the 2 on the 1 computer dc and at random intervals. It could be as quick as the loading screen or up to 5 mins when I get rockin'.

Not sure if this is PC based but it is almost like someone is logging in somewhere else and booting me off the server. I am not lagging or having any FPS issues.