When setting up a proxy server, peculiar error

opensuse 13.1
linux 3.11.10-7-desktop x86_64
gnome 3.10.2

I am connecting to a Squid proxy server on port 3128. When I press “Test Proxy Connection,” I get the following message:

An unknown error occurred during the HTTP proxy test.
Proxy return code: .

I cannot tell if the proxy setup is working.

I have the same problem.