When a human task is opened in BPM Workspace, it will try by default to connect to either localhost or the server's alias. So if you try to access the BPM Workspace remotely (from a computer other than where Oracle SOA is running) you will get an http error (unable to connect).
You can fix this issue at run-time using the Enterprise Manager (EM). Login to EM and from the farm navigator select your composite by expanding the "SOA", "soa-infra" and your partition node. Read the complete article here.
For regular information on Oracle SOA Suite become a member in the SOA & BPM Partner Community for registration please visit www.oracle.com/goto/emea/soa (OPN account required) If you need support with your account please contact the Oracle Partner Business Center.