We are currently using a Cisco ASA 5510 with a CSC SSM module for our firewall. When trying to get to a certain site, we get a "503 Service Unavailable - Unable to connect to IP" error. If I connect a laptop outside the ASA I am able to reach the site without an issue. I've completely disabled all Web scanning/blocking, and the problem persists.
DNS info seems to be fine, as nslookup shows the same IP address whether I'm behind the ASA or not. Ran "wget" from a Linux server and get the same result. It shows that it connects to the site, then says "Waiting for response". After about a minute or so it gets the 503 error.
We've had minor issues occasionally with getting 503 errors on sites since installing the ASA, but usually refreshing the page fixed it every time. With this particular site we get the 503 error every time.