Thanks. It seems you are running 8.0.35, indeed.
Since you say you aren't specifying any proxies in Manifold 8 manually (check Tools - Options, Proxy Server, the 'Connect via proxy server' checkbox should be turned off, report whether it is turned on or off), there must be one set up system-wide. Could you check (a) the values of the HTTP_PROXY and HTTPS_PROXY environment variables (launch a command-line prompt, then run 'echo %HTTP_PROXY%' and 'echo %HTTPS_PROXY%', observe the output - or run 'set' and locate HTTP_PROXY / HTTPS_PROXY in the list of environment variables, post the output of either method), and (b) proxy settings in Internet Options (see the screen on how to reach them, post your screen of the final 'Local Area Network (LAN) Settings' dialog).
Click on the image above to expand it to full size. The description: launch Explorer, navigate to Control Panel, type 'internet' in the search box on the right, click Internet Options on the left, click the Connections tab, click the LAN settings button, done, we are now in the proxy settings (post them).