[ubuntu-uk] Firefox 3 bookmarks

[Mac]

I've just discovered that Firefox 3 does not allow the user-defined 
'browser.bookmarks.file' setting for pointing to a bookmarks.html 
location.  With Firefox 2 and Iceweasel I have the bookmarks on a 
network drive, so I can use the same bookmarks regardless of which 
computer I'm using around the house.  (Ditto my Thunderbird profile). 
The change in FF3 completely messes this up.  Arrghh!

Can anyone advise how best to revert Hardy to Firefox 2?

TIA

Mac