I have been trying to catch this bug on fraps too, but no luck. However, Raxxnamus has got it! This is another reason I have been having trouble tanking. Watch his death runes carefully. See how even when trying to use an ability, it doesn’t work, yet there are death runes ready and waiting.
Update, I later got a video of a rune error at 0:56 in this video.



Had it happen a few times on live as well, very, very rare maybe for a few seconds a night and seems to only be in areas of high lag (ICC after reset generally)
Never managed to catch it on video though! Good find to help us get that fixed
I have had it happen on live many times in ICC. It apparently happens when you got lagged and death runes were generated.
Twitter: gravitydk
Reported it in beta forums too. I know there used to be a bug with them on live, but hadn’t seen it happen for ages.
Twitter: gravitydk
I did get a video of a rune error, added to the OP.