I have been having error 503 codes for the last 24 hours, lucky me, just when I was completely rebuilding two of my sites.
I just kept refreshing and re saving, always a good idea to copy paste your article before publishing, just in case an error wipes you entry.
It seems to be system wide, I'm curious if it's something to do with blogs that have a www.something,com address instead of www.something.blogger.com, i only seem to be having problems with the two that have a custom domain name.