All computers in a company uses Windows XP SP3 and are connected to an AD on a Windows Server 2003. It takes about 1 minute to start Outlook 2007 or Word 2007, but Excel works fine.
If you disconnect the network cable, Outlook and Word start up in a few seconds.
An other problem with the same issue is if you try to change path for templates in Word. It takes about a minute just to open the path window, but if network cable is disconnected the windows open directly.
I've tried with different Anti Virus programs to see it is not a problem with the AV.