Hello, my name is Dan.
I will do my best to help you, the only stupid question is the unasked one.
One thing that does work most of the time is a combination of things.
Repairing Permissions, doing a SafeBoot (runs UNIX maintenance routines on logs and caches) and then trashing the iMovie plists.
This has worked for me with this issue.
The imovie plist is located following the path below, note iMovie must not be running for this or it will not work.
iDVD plist could also be trashed and not hurt anything. They will create new ones, it will not affect or lose any projects or events.
To do a Safe Boot, restart and before the first chime press and hold the 'Shift' key.
Wait until you see the Apple logo and the spinning gear appear, then let go.
It can take as long as 20 minutes to load, so please be patient.
When the login screen appears it will say in red on the login window 'SafeBoot'.
Now login and give it a few more minutes to finish loading.
Try doing whatever it was it was giving you the problem. If it works then probably the problem is solved, so restart normally.
If the problem persists then restart normally also, other fixes will need to be done.
Try that and then try what you are doing and see if there is improvement, let me know.