When a rare spawns that has the zone wide skull vignette the first time my mouse hovers over it it will grow in size like crazy.
It'll show the tooltip for the rare and its loot table, then it will duplicate the text in the tooltip, then duplicate again, then again.
It'll do this for a few seconds until the tooltip grows so large all I see is the transparent background texture covering the entire map.

Hovering my mouse over the vignette again fixes it.
Doesn't give me a LUA error or anything, and it only does it on the zone-wide vignettes the first time I mouse over it. I do use other addons. I do use Rarescanner and Handynotes too so my map was filled with crap and I couldn't tell which one was causing it.

It doesn't look like a Silverdragon tooltip at first, but it is.
My handynotes does not show rares in DF only treasures and the Rarescanner tooltip is stacked on top of that one in the screenshot, which uses a completely different design.