Yo John,
I started out with the iMovieHD 2006 program prior to my oldest daughters wedding, then, in 2012, upgraded to iMovie '11 (version 9.0.9) prior to converting many (35+) family video tapes from analog to digital, then downloading into iMovie '11. Started having problems with program suddenly cutting off, as well as not being able to "share" with anything - project would process so far and then suddenly quit - this would happen early on in the process or after 90% of the project had been processed. I called Apple Customer Service ( thankfully I have an extended warranty on my computer ) who first checked out the computer, then transferred me to their iMovie expert. After 6-8 hours on the phone (I used up all my monthly minutes) over 3 days, I upgraded my OSX Lion to OSX Maveriks (version 10.9.1) and upgraded iMovie to iMovie 10 (version 10.0.2). I did this because by the expert said that my previous OSX (Lion, version 10.7.5) ran iMovie 11 using the internal RAM in a way that was overwhelming the internal RAM - I had already downloaded several video tapes into the iMovie program. Apple told me that iMovie 10 - the new iMovie program - was not compatible with Lion- only with Maveriks - and that the new iMovie program utilized internal RAM ( I have two 4 G RAM chips in my iMac, purchased in May 2012 - soon after Apple discontinued the iDVD program - another story for another time ) differently than Lion - apparently having the ability to access both RAM chips.
I download my VHS tapes into a LaCie 3T external hard drive to avoid depleting my internal hard drive memory capacity. I periodically copy this external hard drive to another LaCie 3T external drive to avoid the dreaded catastrophe of a failed hard drive destroying many hours of labor ( too paranoid?? ).
So far, so good. Apple Customer Service is excellent. I love the new iMovie program - at least until I experience another "bug". The N.E.D. tutorial on both iMovie 11 and iMovie 10 is very good, but does not discuss how to deal with every problem that can come up. The Missing Manual for iMovie 11 was also very good. The Missing Manual for iMovie 10 comes out in April of this year. It will be interesting to see if they describe how to deal with the various problems that have appeared in iMovie 10.
Please forgive my lengthy diatribe and possible inaccurate use of technical terms ( eg. RAM chip? ) , but maybe this will help someone else having similar problems with iMovie 10.
Hopefully I will be able to use my iDVD program with iMovie 10.
Take care, Benn Haynes, Bellingham, WA