SolidWorks 2013 introduced a new process for opening files called SolidWorks file launcher (SWShellFileLauncher). This process is normally associated as the default application for opening SolidWorks file types. When a user double-clicked (or right-clicked) a file to open it into an existing SolidWorks session the following errors could occur.
Previously the only work around was to try opening the file into a new session (required user to close existing instance of SolidWorks), drag-and-drop the file into the existing session, or use the File Open menu in the existing session.
SolidWorks recently released SolidWorks 2014 SP0 and SolidWorks 2013 SP5 which includes updates to the SolidWorks file launcher which eliminates the errors above from occurring.