HTTP 504 Errors in SharePoint

I have some users are experiencing HTTP 504 errors in SharePoint. This is occurring when they just connect to the actual SharePoint site. Internet Explorer is just displaying a generic error message 开发者_StackOverflow中文版but I captured a more detailed error through Fiddler. The result was this:

ReadResponse() failed: The server did not return a response for this request.

The user can either wait a few minutes or refresh the page a few times then everything will function normally again. Has anyone else experienced this?

HTTP 504 is Gateway Timeout:

The server, while acting as a gateway or proxy, did not receive a timely response from the upstream server specified by the URI (e.g. HTTP, FTP, LDAP) or some other auxiliary server (e.g. DNS) it needed to access in attempting to complete the request.

Looks like a connectivity problem to me, probably DNS. Nothing to do with the software. You might have better luck on serverfault.