Problems with Chameleon and Firefox

I have the weird problem that font ascenders (like German Umlaute) and descenders (like y, g) are cutted inside TextField when I use the chameleon theme and Firefox. In IE and Chrome everything is fine. The effect also changes slightly if I omit the caption. I don’t understand what’s going wrong there, because I only use simple vertical layouts and it’s only broken in Firefox. I added a file with screenshots so you can see what I mean. I use Vaadin 7.0.3 on Win XP.
Can anybody imagine what might goes on there or has a suggestion how to examine the problem?

No reaction here yet. In the meantime I could melt down this problem to a very short and simple example to prove that this seems to be a bug in Vaadin 7. I created a bug report in trac for it.