This is probably the same as the IE9 CSS issue, so sorry if I should have responded there.
I may be oblivious and have overlooked this issue until recently, but today I opened http://mercurial.selenic.com/ and the fonts on all the H? tags are double entered and the menu looks to have the same problem.
I'm using IE10. Switching to comparability mode causes the page to look correct.
The IE9 CSS issue reported previously said that text was rendering upside down. I'm not seeing that. Everything is just doubled in two different fonts.
Looks fine in Chrome.