I've started rolling out XP Pro to my mobile users. They previously had access to OWA (Using IE6 to reach an E2K server), but after SP2 was installed, they don't. There is no login presented, only "The page cannot be displayed."
Our site name is in the Trusted list, pop-ups are allowed for the site, too. All the W2K clients have no trouble accessing their mail with OWA and IE6.
I've read the Known Issues document at MS, along with "The Impact of Windows XP SP2 on Outlook Web Access" from Messageware, but we're not experiencing any of those errors.