|I'm wondering if it is CCleaner clearing the DNS cache that is temporarily fixing this.|
It's a long shot but can you try disabling the DNS service please. You have to first Stop the service, then switch it to Disabled - like this:
Best restart the computer and give it a good test. If it doesn't help set it back to Automatic and set it to Run the service (it will run anyhow on restart).
Always pop back and let us know the outcome - thanks
message edited by Derek