error connecting to Robosource 3

We are trying to set up Robosource 3 to support multiple writers. Until recently, there was no need, so the project has resided on local drives. We just upgraded to Robohelp 6.

I have installed Robosource 3 and SQLExpress on the server (a virtual machine, actually) and set up the database, but whenever I try to connect the local (client) to it, I get the following error:

Object reference not set to an instance of an object.

at SCCAPI.SCCIMPL.SccGetProjPath(Int32 context, Int32 hwnd, String& user, String& ProjName, String& LocalPath, String& AuxProjPath, Boolean bAllowChangePath, Boolean& bNew)

Any assistance would be greatly appreciated.

Thanks