The http proxy server seems to strugle on sites like www.amazon.com? Half of the page loads and then the browser just hangs. Looks like amazon/proxy holds the connection open even though all files have been received. Refreshing the screen causes the page to display fine (presumably because the browser now has all the files in cache?). Moving to another unvisited page causes the problem to occurr again. No exception is raised and if you leave the browser eventually the page is displayed (after 2-3 minutes it seems which is probably the receive timeout?).

Any ideas how to fix this?

The Proxy does not handle Http1.1 requests gracefully. In Http1.1 a connection can have multiple requests to different hosts. You need change the destination socket if the host has changed on the same connection in the OnClientReceive method. When you refresh you are effectively sending a new request on a new connection and so it works. If you shut off Http1.1 things will work also.