Are snapshot and varnish cache incompatible?

I am getting this error during the plugin part of the backup process: Error 503 Service Unavailable
Service Unavailable
Guru Meditation:
XID: 1101490158
Varnish cache server

It seems to be a development as of the update before last of snapshot. Because of the way one of my directory plugins works, I must back up my plugins to be sure that if the directory is ever hosed by an update I do not have to redo it from scratch. I am hosted on Dreampress at Dreamhost and so I cannot turn Varnish off. It is part of the deal. . .

Is there anything else you can think of that I should check. Again, I was able to use Snapshot about twice a month without error and with the same settings up until the update before last.