Keep getting "You don't have a valid Steam subscription for this application [AppId=6000]"

[DaCliff]

Hi.
Just bought the Star Wars Collection and installed Republic Commando.
Problem is each time I try starting the game I get an error message saying "You don't have a valid Steam subscription for this application [AppId=6000]".

Is there a problem on my side or is this a Steam issue?
Running on Win7.