The following is a set of steps to help debug why a user can not connect to FBS application from a client workstation.

Server

Check that foundation is running on the server machine by connecting locally

Workstation

Check version of Java
Run javaws  and go to About -> Help.  The version should be at least Java 1.5.0_05.  If it is not install the correct java version from User Setup for Accessing Business Suite.
Turn on the Java Console
Run javaws and go to Edit -> Preferences and select the Advanced tab.  Expand the Java Control tree and select the Show Control radio button. This will now start the Java Console when the Application is run.