firefox JS problems in FC6

[sbeam]

I have been developing some web apps with DHTML effects on my FC6 
system. But it seems FF is broken with respect to certain draggable and 
opacity effects on this platform. Here is an example:

http://script.aculo.us/

On FF 1.5 on Win and Mac I see 4 large circles which can be dragged 
around. On Linux, nothing but green space.

Does anyone else notice this, or is it just me? I am running 32bit FF on 
a x86-64 system. Other than that its all stock with a few common 
plugins.

thx
Sam