Comment # 3 on bug 1210208 from Fabian Vogt

(In reply to Tom de Vries from comment #2)
> (In reply to Fabian Vogt from comment #1)
> > Which applications?
> 
> - firefox, when clicking on bookmark folder.
> - Konversation (as in konversation, entering text is slow).
> - thunderbird (highlighting of entries in menu: new/edit/find/print etc).
>   Likewise in firefox.

Ok, so not a Plasma issue. The common denominator is X here.