I have managed to reproduce this (at least I think it is the same issue). Only for me, it happens when I drag and drop a channel in the lists. When I drop the channel, the list on which the channel gets dropped appears to be cleared. In fact it is not, the items are still there and you can still click on them (an do what they are supposed to) but they are blank.
I will take a look and see what I can do.
Mantis entry: 0002811: Dragging a channel in any list in TV Combinations causes the list to stop painting - MediaPortal Bugtracker
I will take a look and see what I can do.
Mantis entry: 0002811: Dragging a channel in any list in TV Combinations causes the list to stop painting - MediaPortal Bugtracker