My iPhoto library is on my network share which has not changed.
That's the problem.
iPhoto needs to have the Library sitting on disk formatted Mac OS Extended (Journaled). Users with the Library sitting on disks otherwise formatted regularly report issues including, but not limited to, importing, saving edits and sharing the photos.
You've been lucky that it worked till now.
You are right about the network share. I put the movies on my mac mini server and was able to import them into iPhoto running directly on the server. Pretty odd though since the share is AFP on an external disk formatted Mac OS Extended Journaled and had been working great all this time with no changes in the network or sharing. I'm guessing something Apple slipped into an update may have broke it. Oh well, guess I'll have to keep importing movies on the server itself from now on.