linux-firefox vs. linux-gtk2

[mi at aldan.algebra.com]

I installed linux-firefox-3.0.19,1, but it refuses to start-up beyond 
the little GUI message box, that tells me, my GTK+ is too old, and that 
version 2.10 "or newer" is required. Mine is the latest available from 
x11-toolkits/linux-gtk2 -- the 2.6.10_4.

This is a 7.1-STABLE/i386 system from Jan 6, 2009 -- it is too far from 
me physically to undertake a full upgrade. Its (non-technical) user 
wishes to be able to access YouTube videos, which requires Flash...

Any advice? Thanks,

    -mi