In June, Microsoft adCenter postponed maintenance, but it appears that it's about to happen. adCenterEU posted on WebmasterWorld, DigitalPoint Forums, and Search Engine Watch Forums about upcoming maintenance to be held on Saturday, July 14.
Microsoft adCenter will be unavailable during an upgrade this Saturday, July 14, beginning at 10:00 A.M. Pacific Time (18:00 P.M. GMT), and continuing for up to 14 hours. During this time, your current keywords and ads will continue to run normally; however, you will not be able to access adCenter.
Please make any needed changes to your account beforehand if possible.
After the scheduled maintenance, reporting may be delayed for up to 24 hours. On the adCenter Reporting tab please check the timestamp at the bottom of the page to see when the data was last updated.