Thanks - tried that. Perhaps a bit of background:
1) Did clean install one month ago, used Autoupdater to load majority of updates, then MS Update. Loaded Java RuntimeEnvironment_1.5.0.10. Did not test website at this time.
3) 3 weeks ago installed RevIQ Real Estate software (www.reviq.com) - software installed some variation of SQL during install.
2) 2.5 weeks ago, discovered "favourite" website not working. Upgraded IE to 7 and WMP to 11 (just because...).
4) Yesterday, in conjunction with help from tech support at website (aucsat.co.nz), discovered that Microsoft VM not installed (no idea how that happened). Uninstalled RevIQ, ZoneAlarm, IE 7 and WMP 11. Installed MS VM 5 from download and updated from MS Update. Still no joy.
5) Today. Discovered that making new user fixed problem.

Questions:
1) How could MS VM get "uninstalled"?
2) Since the aucsat page is aspx with Java on it, and MS VM is now re-installed, why no go?
3) Why does a new user fix what appears to be a system-type error? i.e. not a firewall problem
4) Is it possible that the RevIQ SQL (even though now uninstalled) changed something only in the one user account?
5) Could some setting have been altered using Autoupdater that would have caused a prob? Note that I used the same update procedure on 2 other machines (both running XP Pro SP2 - one P4 2.8, one dual AMD X2) and they have no probs (and both are also running IE 7 and WMP 11).

Thanks