It's not any help, but I'm receiving the same when I access my Wordpress blog hosted on Boru. I've noticed this for a while becoming more frequent since maintenance at beginning of April (could just be coincidence).
A 503 error indicates the server (running the Web site) is currently unable to handle the HTTP request due to a temporary overloading or maintenance of the server. The implication is that this is a temporary condition which will be alleviated after some delay.
This could suggest a capacity issue on the server.
Alan