I thought that posting my experience just now might be helpful to others.
Yesterday (25-Aug-2009) my Outlook 2007 was working perfectly. I had downloaded & installed Outlook Connector 12.1 because I'd received an e-mail from Microsoft to say that the DAV protocol used for HTTP mail would be withdrawn on 1-Sep-09. I also noticed that MS had restored the POP3 service that they closed down a couple of years ago.
So I set up the POP3 account and started working with that. All OK.
Last night when I closed down, Windows Update came in and completed on reboot this morning. Outlook 2007 wouldn't start, coming up with the message: Cannot Start Microsoft Outlook. Cannot open the Outlook Window. The set of folders cannot be opened. The information store could not be opened..
Nothing I did in that environment would enable Outlook 2007 to load, I created a new profile and that did no good.
So I went back to the System Restore Point made at the time of installing the Outlook Connector and everything sprang to life.
I had also tried the restore point that undid the Windows Update, but that didn't cure the problem either.
So, I'll see what happens when I reboot next time in case it had nothing to do with Windows Update.
Cheers to all.