I have run into another issue with SharePoint 2007 which specifically only affects Office 2007 running on Windows Vista.
We have SharePoint setup using ISA 2006 for forms based authentication. This works perfectly for XP/2003 with Office 2003/2007 and Vista with Office 2003. However when we open a document from SharePoint 2007 using Office 2007 on Vista, we are prompted for a password. This is rather annoying. I have opened a call with Microsoft to see if I can get to the bottom of this.
There are numerous articles out there saying that this is to do with IE Protected mode, but we have this switched off for the Intranet zone (hence it works fine in Office 2003 on Vista).
Even more worrying than the simple inconvenience of the prompt is that fact that WebDAV caches the users' credentials. Imagine the scenario that you go to a public access machine and log onto SharePoint using ISA FBA. You then open a document and enter your credentials. You then finish working and log off Sharepoint and close the browser. You would think you were now logged off, but you are not as WebDAV is still caching your credentials. Whoops!
Following my call being escalated by the good guys at ESK UK to Microsoft, it has now been escalated within Microsoft. I've just been on a call with a very helpful escalation engineer at Microsoft who has confirmed that this issue is related to Office 2007 on Vista trying to use WebDAV and WebDAV trying to authenticate using Windows Auth, rather than using the persistent cookies. As our server is connected via ISA using FBA, Windows auth falls back to basic auth and then WebDAV caches the credentials (until the webclient service is restarted or the user logs off).The engineer has provided a useful workaround: install the Web Client update for Vista (http://support.microsoft.com/default.aspx?scid=kb;EN-US;907306) and then set all Office Apps to run in compatibility mode. This has a couple of drawbacks other than the work involved. Firstly it loses the enhanced ability that WebDav has to be able to browse up and down SharePoint web applications and secondly it does not resolve the password prompt you get when when you try to use Explorer view (I don't know of a way of telling Explorer to run in compatibility mode). Nevertheless we will use this workaround on the few Vista machines we have, but will certainly have to think twice before rolling Outlook Vista and Office 2007 to our 12,000 desktops.
The following registry keys can be set to tell Office Apps to run in XP SP2 compatibility mode. Remember you can really mess up your machine by changing the wrong registry settings so back it up and go careful: