Missing text on Gnome/GTK apps

[Mole <mole bigwig net>]

I have Gnome installed with RedHat 6.2. All used to be fine, but now text is 
missing from gnome/gtk apps - right down to gcalc.

The menu bar and buttons have no text.

I've put a screengrab up at http://www.bigwig.net/mole/gcalc.gif

I've reinstalled xfs, and all the XFree86-fonts, but couldn't find any fonts 
supplied with Gnome or GTK (these might not be in xfs's path list)??

Other stuff including KDE apps and Netscape are fine.

Its the same whether I've switchdesk'd into Gnome or KDE.


Any pointers would be greatly appreciated


Cheers
Neil