Some time back I had an issue with a SP2007 site. Users were getting the Access Denied error in the front end site. I couldn’t even log in with a Farm Administrator site! I could get to CA though. I spent days searching and trying different things, messing with permissions, etc. Eventually I stumbled upon a page with information about the SetSiteLock feature.
So I check the site lock setting with this script:
stsadm -o getsitelock -url http://server_name
Lo and behold it was set to readonly, which makes you think that you could access it. In this case however, no one could access it! So when I set the SetSiteLock to none, it was fixed. So I found that while the server was performing a backup, Windows Update came along and applied updates. Naturally it kindly restarted the server for me, leaving the site in Readonly (but somehow locked) status. Since the powers that be would not let ME control the Windows Updates, I scheduled backups to NOT coincide. I’ve never had that issue come up since.