http://www.uscis.gov/portal/site/uscis/menuitem.5af9bb95919f35e66f614176543f6d1a/?vgnextoid=a5b0a083ef5b3110VgnVCM1000004718190aRCRD
Scheduled System Outages
On Thursday, July 12, 2007, at 9 PM EDT, certain USCIS web-based systems will be taken out of service for maintenance upgrades. They should be restored in approximately three to four hours. These systems include:
Case Status Online (and processing times)
Field Office Locator and Information
Civil Surgeon Locator; and
Change of Address Online
We apologize for the inconvenience.