Hi, thanks for taking the time to help me out!
I agree 100% with your assessment. I also thought of just installing the library manually but it does say on the Processing.org website that "The Video and Sound libraries need to be downloaded through the Library Manager. "… I guess I’ll try to do it manually anyway and see what happens!
Otherwise I’ll try @GoToLoop 's suggestion. If it works that way, I guess that will mean there’s some strange issue with the specific Processing release I’m using and whatever is going on with my computer.
Thanks all, I really appreciate the help!