Unexpected element: TAG_END

I'm having the same issue, the only thing I've been able to check is that this is only happening when I'm behind a proxy, if I get direct connection to the web it works ok, however I change connection to be behind a proxy, configure the proxy connection page, check that the starter page works ok (that's it, I'm connecting to the web behind the proxy), it stops working.

Did you get a solution for your problem? how?