http://bugs.winehq.org/show_bug.cgi?id=24485
--- Comment #4 from Jukka Tastula poltsy@gmail.com 2010-09-21 13:01:57 CDT --- Can't see it happen anywhere in the vanilla ui, or maybe it's just not that obvious. Like the bisect says this apparently started happening a while ago but I've been only playing beta without addons and haven't noticed.
All I need to do to reproduce this is run the game in d3d mode with ShadowedUnitFrames ( http://www.wowinterface.com/downloads/info13494-ShadowedUnitFrames.html ). No special addon configuration needed. Just target an npc that doesn't have any mana/energy/rage.