Are you downloading through the update service? If so, try downloading directly from http://www.mozilla.org/en-US/firefox/new/, close Firefox, and run the installer

Thanks fmdeveloper, doing the same as with the auto upgrade. The time remaining goes up and up, 20 min and counting, while the rate of data transfer is ridiculously slow. Could be a problem in my system but everything else is working fine and a speedcheck was consistent with previous tests. Think I'll wait out this version and try again for the next upgrade.

You could also try downloading from the FTP site -> ftp://ftp.mozilla.org/pub/mozilla.org/firefox/releases/7.0.1/win32/en-US/

That was too easy fmdeveloper, and done in the usual few seconds. While Firefox Setup 7.0.1 went through in a jiffy, a second file, Firefox Setup 7.0.1.exe was trying to download at a crawl which I aborted. The upgrade works perfectly, your help much appreciated.