Fix separate proxy login prompts for http and https on Safari?

[pete]

On our macs, which use a proxy authenticating via ntlm, the kids (who are using a shared account for the macs - not my idea) get one proxy prompt when using Firefox.

If they use Safari, they get a prompt for http access and then another prompt the first time they attempt to use a https site.

Is there any way (besides "use firefox") that I can make Safari only prompt the once? I've tried manually entering the details and also using a proxy.pac - both exhibit the same behaviour. I suspect it's due to safari not having a "use this proxy for all protocols" option, like other browsers.

[DMcCoy]

If safari stores http and https as two entries in the keychain then it may not be possible.