As it happens I was respinning Fedora 7 when I checked back here! Yes, it would appear that rebuilding the whole distro solves the problem, but I can't help thinking that I'm using a sledgehammer to crack a nut.
This is i386, but I'll need to respin the x86_64 version too at some point (I have over 150 i386 boxes to reimage in the next few months - mostly with e1000 cards - and 30+ x86_64 boxes arriving shortly). I'll keep checking for a simple solution, but until then it's good to know there's *A* solution out there!
Cheers, G