Using External Drives with iMovie Libraries

I have searched far and wide for the answer to this question. Maybe someone can help. I have 2 Macs with a Buffalo 3TB External HD connected USB to my Time Capsule. I moved one of my iMovie libraries to the Ext HD. iMovie will not open that library now because the format of the selected drive is not supported. The HD was properly formatted to mac iOS journaled before using. I tried a terminal a command (defaults write -app iMovie allowNV -bool true) recommended in several different forums saying it would allow access to network drive from iMovie. Didn't work. What am I missing here?

Thank You