The bug appears to be somehow related to XFree86-4
event handling; XFree86-3 servers are not affected. The
most clean visible bug example is XVMahjongg
application (in -b mode, -c mode is already broken by
CMS). When you remove first tile pair, the whole game
field is never redrawn again. Similar behavior seems to
be exposed by xview-lib-extras/libguide/demo/xview/tree.