Just wanted to share this. A very enterprising person posted this in the Bug Report Blizzard forums. Link
Deyneth made up scripts for 2 macros, the first of which you'd use whenever there might be a possibility of freezing the game. I'd recommend turning off the tooltips whenever going into a random dungeon, like when zoning into the Oculus, your mouse naturally lands right on the entrance portal, causing the freeze-up. Also, definitely do it when going for the Headless Horseman. The first script will still allow you to interact with objects, it just won't pop up a tool tip description when you hover over them.
And, when the danger has passed, like after you've killed the HH, use the second to turn tooltips back on.
I've taken the liberty of posting the scripts here as well. Copy & paste into macros for your toons, and you shouldn't have any problems. /cheers for Deyneth!
Turn Off Tooltips
/script GameTooltip.Temphide = function() GameTooltip:Hide() end; GameTooltip:SetScript("OnShow", GameTooltip.Temphide);
Turn On Tooltips
/script GameTooltip:SetScript("OnShow", GameTooltip.Show);