I folks, an update to the saga, I'm back on 0.9.3 of firefox. I simply couldn't get round the updated Firefox1.0 blocking of sites to install software of ff1.0.
Now I don't know if this is my setup, also lean (InTheWild) and I'm not running SP2 either, but having gone back to 0.9.3, I think I have found a flaw in the Install Software blocking.
I did the usual uninstall, reboot, install of ff1.0, removed all incompatible extensions and tried again. The link (url) path when you click points to update.mozilla.org (which I added to the allowed sites), this however is a redirect link and the actual download/install url is http: // ftp dot mozilla.org/pub/, etc. etc. so ftp.mozilla.org is not on the list of allowed sites.
So when the block warning comes up and you are allowed to get into the settings to allow the site, the url that is added to the list is update.mozilla.org. However, the file is actually downloaded and installed from ftp. mozilla.org, so it is blocked and the loop continues, offering to allow update.mozilla to be added to the list.
So this issue could be a problem with other sites that use a redirect link to the software.
Now waiting a resolution from a non PR (Preview Release) of firefox 1.XX. I could also add ftp dot mizilla.org to the allowed sites list or remove the sub domain reference and only having mozilla.org in the list so that all subdomains of mozilla.org are accepted (I don't know f that would work).