I assume you are using IP Addresses and not the DNS name of the PC? Make sure you have the right port appended to the address in your web browser. I like to use either FF or Chrome when running it. Have not had any issues using the IP of the server PC with the correct port on the same internal network and connecting with multiple computers throughout my home.
Try also 'pinging' the computer that has Vibe Streamer installed from your other computers and see if you get packets back.