I had a similar problem with fonts doing that, and other strange things (some other fonts were very choppy), a few days ago, when I tried to change the fonts.
I had just installed KDE 3.2 on Slack 9.1, I ended up editing my qtrc file in ./qt under my /home/<user>, I just removed the reference to
saved it, logged out (I think I also restarted X for good measure), and away I went. For some reason there was also a line in there about embedding the fonts, I removed that too as it hadn't been in there before I started changing the fonts.
Apparently, I could also have run qtconfig (I emailed the maintainer of the contributed packages) - I did run it just to see what it does, and I think it would have accomplished the same thing.
Hope this helps.