Hi, I'm from the same IT dept as Lerswin, thanks for the responses so far We would have responded more if this specific thread wasn't blocked by our LEA (heavy-handed keyword filtering, we think....)
To clarify the situation - when users access the internet, the proxy box (a Cachepilot) authenticates them locally via a second logon. We previously had the Cachepilot authenticating transparently through AD, but this caused problems with the Cachepilot when we altered users' AD group membership on the fly so as to change their level of web access (e.g. banning students, or elevating there access in some cases).
The way we are set up now is that the school students log on to the web using a generic shared username, authenticated on the Cachepilot, and receive whitelisted access. They have mandatory profiles and whether or not IE8 remembers their credentials (it doesn't, of course) is not an issue.
College students and staff log on to the web using unique credentials, authenticated on the Cachepilot, and receive various levels of blacklist filtered web access. The students have mandatory profiles, and again this problem is not particularly an issue for them. The staff have normal roaming profiles, with app data included. I would expect IE8 to store their credentials if they tick the "remember my password" box, but once they relog, it's gone.
My immediate thoughts were that it was a profile issue, but the curious thing is that Firefox (3.5.x) remembers staff credentials just fine. I've also tried setting up a pc with IE7 and that works fine with a staff test account too.
Apart from wishing we hadn't bothered rolling out IE8, I'm a bit stumped with this one!
Thanks again for any thought anyone might be able to offer