Installing XForm.xpi throws error

Fedora Core 3/Gnome

I downloaded the nightly build, as stated on the XForms page. Installed 
it in my home/bin folder, I didn't want to install it over my current 
Firefox version. Started it through command line, went to Xforms page to 
install the XPI, clicked the link, got the usual install extension 
window, clicked install now got a Download error prompt. Also got this 
error in the shell window:

*** loading the extensions datasource
*** getItemProperty failing for lack of an item. This means 
getResourceForItem                 failed to locate a resource for 
aItemID (item ID = 
http://ftp.mozilla.org/pub/mozilla.org/extensions/xforms/beta1/linux/xforms.xpi, 
property = disabled)
*** getItemProperty failing for lack of an item. This means 
getResourceForItem                 failed to locate a resource for 
aItemID (item ID = 
http://ftp.mozilla.org/pub/mozilla.org/extensions/xforms/beta1/linux/xforms.xpi, 
property = internalName)

Is this due to the fact that I didn't uninstall Firefox 1.0.1?

Thanks for helping me out,

Marc Campeau