Runing a Snitz forum using Access database we are getting the occasional error message 'Service Unavailable'. It is difficult to replicate but does tend to come whilst browsing the forum. Our database is in excess of 30Mb.
I suffer from this problem from time to time, I think Podge is correct it is a server problem, although as yet I and my hosting co have not come up with an answer. My database is only 14Mb in size.
it sounds to me like the IIS service is recycling possibly due to an error on a different site which is why it is so random, get your host to check their eventlogs, that is what they are for