Dealing with a sudden access denied situation on some of the sites on our dev farm.

This morning we suddenly found that we could not access the top level site of our dev site collection. In fact, we have found there are quite a number of other sites we cannot access. We have yet to find any user who is able to access the top of the site. Farm admins, site collection admins, etc. all get access denied to the top level.

The farm has 3 site collections. The root site collection prevents us from seeing the top site, but at least one secondary site on the collection is viewable by those with permissions. Another of them appears to allow the top level and a number of the second level sites - the ones we have had time to check.  The third site collection allows us access to the top level, but we have not found any second level sites that we can access.

I really am having a tough time figuring out any pattern.

There is nothing obvious in the event or ULS logs that correspond to the access denied messages.

I have seen, on the net, references to issues with the portalsuperuseraccount and the portalsuperreaderaccount values.

I ran commands to set those to the proper values.  No change in the behavior was seen. And I would not expect those to cause sporadic problems - I would think that nothing would be accessible rather than "random" sites.

Do you have any ideas what might be be able to be done to fix such a thing?

Thank you