This usually means port 3200 from the /../..etc/services is not connecting to your backend. Can you telnet from the PC with the issue via port 3200 to the backend IP address? If not, verify your PC's firewall isn't active and if you are in a domain with a firewall then that port will need to be authorized.
I am surprised ping worked? That was typically used in Denial of Service Attack's in the late 1990's. Most Network Security Admins will lock that down.
Other suggestion is to move on to SAP GUI 7.40 Patch 4 Hotfix 1.
Cheers,
Dan Mead