Solid FFMPEG in background worker fails on user pc

I'm using Solid FFPEG to rip out individual frames from a video, I'm using this to 'play' the video (so it rips out each frame). I'm using a background worker to keep the UI responsive. Running on my PC I have no problems, but on the test PC it will not display the frames, I get the below error from the background workers RunWorkerCompleted method.

System.InvalidCastException: Unable to cast COM object of type 'System.__ComObject' to interface type 'CAVEditLib.ICAVConverter'. This operation failed because the QueryInterface call on the COM component for the interface with IID '{59C19DEF-02ED-44CD-BFD8-2FD09DBDC9F9}' failed due to the following error: Error loading type library/DLL. (Exception from HRESULT: 0x80029C4A (TYPE_E_CANTLOADLIBRARY)) at System.StubHelpers.StubHelpers.GetCOMIPFromRCW(Object objSrc, IntPtr pCPCMD, IntPtr& ppTarget, Boolean& pfNeedsRelease)
   at CAVEditLib.ICAVConverter.get_AVPrope()
   at RoutePlotter.VideoManager.UpdateAllFrames(Decimal frontNumericValue, Decimal backNumericValue, Decimal leftNumericValue, Decimal rightNumericValue)
   at RoutePlotter.MainForm.backgroundWorker_DoWork(Object sender, DoWorkEventArgs e)
   at System.ComponentModel.BackgroundWorker.OnDoWork(DoWorkEventArgs e)
   at System.ComponentModel.BackgroundWorker.WorkerThreadStart(Object argument)

The cavEditLib.dll file seems to be registered on the Test PC, but the background worker won't work.

Thanks fro any help.