Cheers for the tips. I have now fixed it...
This was my solution, intially went on the SQL server with the DB on to check for any signs of errors... the server crashed.. i brought it back online.
I then restarted the IIS services which removed the http 503 error and led me to some other errors which were long... and were concerned with the reporting and analysis services so
Went to the next SQL server that hosts the analysis and reporting services restarted those and bam it was all working again after that.
But as you said keith i reckon it was to do with that default rapid fail protection limit.