Hi,
We are having problem with OWA and when we are going to access OWA getting like this error.”HTTP/1.1 503 Service Unavailable”. I found that problem. Because two exchange services have been corrupted by immediately power frailer. Then, every user can’t send and receive email. Also windows 2003 is not logging as normal mode and it does not come into view dialog box of enter user name, password. Then, I have to logging as safe mode and stop those exchange services. After that, I have to restart windows 2003 as normal mode and start those two exchange services manually.
Still, Server is not logging as normal mode and doest not appear dialog of user name, password. Because of corrupted services is not able to start automatically while windows 2003 is logging.
See this like for more information
http://support.microsoft.com/?kbid=823159
lasantha