firefox/thunderbird fonts become small. f8/KDE?

[Gene Smith]

This is a bit hard to describe but possibly others have seen it. I will 
be going along with firefox and thunderbird with fonts OK. Then suddenly 
they become both very small. In firefox it is just the menu and toolbars 
that go small while in t-bird, the folder list and message become small.

If I restart X they return to normal expected size. Once they go small, 
only X restarts (or reboot) fixes it. Have seen this with and without 
the package gtk-qt-engine.

I mostly use KDE so not sure if this happens in other environments.

-gene