SnowWitch,
I got the same message as you did.
Turns out I had a folder created in the applications where I put the iMovie and plugins in.
I pulled the iMovie out of that created folder (but still left it in the applications) and ran the update again.
Updated just fine.
Also in the update 'read me' it said the update will update 3.0 and 3.0.1 only.
Also *two* <gr> If you're talking about OS 9xx, think Steve is correct.
Also *three* <gr> It says you need QT 6.1. or higher.
Also *four* ---- /this is the end\