First please try quiting and then starting iVI with the SHIFT key held down to clear out any entries in the queue.
If that fails then please reset your iVI preferences as follows:
1. Quit iVI
2. Open the Terminal App which can be found by opening Finder, clicking on Applications on the sidebar, opening the Utilities folder which will contain it
3. Enter the following into the Terminal App:
If you have iVI from the App Store then enter...
defaults delete com.southpolesoftware.iVI
or if you have iVI Pro from our website then enter...
defaults delete com.southpolesoftware.iVI-Pro
... and the press return (you should see no error)
4. Run iVI