I'm running JWM and I'll drag a window across the screen and it disappears then loads to the otherside like a broken VAXstation. I have 4gb ram, so this is a big issue. Is there a log file I can dump and show you guys?
On window managers which target low resources this might be a feature. At least if it means that the window content is just now shown when it is dragged. I have used x11-wm/jwm some time ago because it requires low resources only. Please check your ~/.jwmrc. It might be the move-mode configuration.