The first thing I test to do when iMovie doesn't behave as it should is to trash the preference file.
It's a very common way to try to solve problems with Applications that has problems.
Reg iMovie that file is named as one or more of these
com.apple.iMovie.plist
com.apple.iMovie3.plist
com.apple.iMovie7.plist
com.apple.iMovie8.plist
com.apple.iMovie9.plist
com.apple.iMovieApp.plist
Not always all of them are present - but many can be
I also trash
com.apple.iApps.plist
and clean out the Cache folder
All of them are in a folder named Library - BUT as there are more than one - most people chose the wrong one.
The obvious one is Library on Root level - first window that opens when You open Your Start-Up Hard Disk.
AND - that is the wrong one
The one to find is the one in Your User Account folder - and in Mac OS X.7 and so on - it is HIDDEN.
Easiest way to find the correct one is to go up to the top row Menu (Apple symbol to the top Left hand corner of screen) and here go to the right to GO and keep Option-key DOWN and it will Show You the correct Library.
Now - here find the folder Preferences to move out the com.apple.xxxxxx files to the desktop WHEN APPLICATION IS NOT RUNNING ! IMPORTANT !
then find the folder named Caches - here too - try to identify the cache files that are connected to the application - and move them too to desktop.
Now try to run Your application e.g. iMovie
There is an easier way to test if this is the real problem by
• Goto Apple menu and down to System preferences
• Select Accounts
• Click on the Plus sign and create a new user e.g. test1
• Apple menu - and down to Log out
• Now log into the new user test1
• Now see if application runs as intended
If so - then the problem to 99% is in the Pref or Cache files.
Yours Bengt W