(More) Tabs do not line up in a popup

When you have more than few tabs in a popup they are not aligned in a single column. Instead, it show up uneven in two columns:

https://www.dropbox.com/s/ezj05nnd7cwm63q/Screenshot%202015-02-04%2009.54.37.png?dl=0

Hmm.  That is certainly ugly.  But I cannot seem to replicate it.  Do you have any custom CSS that would be constraining the popup height?