0: find machine with internet explorer (verified with IE10 on win7, IE11 on win7 and win8.1)
1: open enwiki, log in, activate hovercards
2: hover over a link and make sure card appears
3: stop hovering, see the card disappear
4: hover over same link again
EXPECTED RESULTS: card should appear again
OBSERVED RESULTS: the card appears empty, with height=0. the little triangle is still there, and the upper and lower borders of the card are shown basically merged to one horizontal line.
(repeat steps 0,1,2 from above, for a link to an article with an image):
Notice that the image appears to be broken.
this issue is only verified with IE10 on win7. it may or may not happen with IE11.
Problem captured in this video: