I found this problem yesterday afternoon also. I can not visit my web proxy
http://proxy1china.appspot.com (74.125.19.141). I thought it is caused by GFW instead of Google Bug because I used other proxy tool and I can get my site. Then I add a
subdomin http://168.chinaguideblog.com (72.14.235.121) to bound my web proxy,I can visit the subdomian but http web proxy doesn't work,I thought https web roxy will work but
my domain doesn't have SSL certificate, so I have to stop to try.
This morning,I used OPENDNS,change DNS to 208.67.220.220.
After that,I can visit my web proxy directly but
http://proxy1china.appspot.com doesn't work,
https://proxy1china.appspot.com still works well.