It may or may not be related, but my VPS has been on a roller-coaster of ups and downs starting May29th until June 10th. It seems to have stabilized since then.
One thing I checked was that that a few of my domains had been changed to use FastCGI. I switched those back to just PHP CGI 5.4
I have registered a new domain since then and I noticed a new check-box when setting up hosting , just below the part where you select your PHP version ..that says:
I wonder if there is a new "Automatic Upgrade" feature that DreamHost has put in place. I went through all of my domains and unchecked that feature, since I have had issues in the past with using FastCGi on my VPS and FastCGI seems to be the upgrade path they take when auto upgrading.