We have set up scheduled PRU and Live Update tasks, but they fail...!

Proxy Server Management has been set with the correct IP and port (no
authentication required). Have checked the proxy access from IE on the
same box - all ok.

If I try and perform a PRU 'Download/Update Now' I get the following message:

[2.4.1608] Error communicating with web server stella.tallysystems.com.
Unexpected return code from web server: 404

The Live Update 'Download/Update Now' just says:
'Unable to Apply Product Update'

The only thing I could guess at is that because the proxy server requires
no authenticaion (i.e. no username and password) that the update process
doesn't use the proxy settings because these fields are empty?!? We have
tried enetering a dummy username and password with no joy.

Could it be anything to do with IE hardening on WS2003? We have added
http://*.tallysystems.com; https://*.tallysystems.com into the trusted
sites in IE - does this info need adding anywhere else?

Any suggestions welcome!

Many thanks