My playback screen in iMovie '11 is always blank or a still, broken picture. How do I fix this?

Question

Picture of my screen: http://imageshack.us/photo/my-images/88/screenshot20120623at929.png/
Sometimes it ends up like this: a still, broken picture: http://imageshack.us/photo/my-images/688/screenshot20120623at929.png/
I don't know what happened. It was fine until I tried to play back a video I was making and it didn't want to. Imported videos play fine, but when I drag a clip to the editing part it doesn't play.
I also made a short project a while ago, but no matter what I tried I couldn't delete it. I also couldn't play it again or even access the editing screen
I don't know if I imported too many videos, or have too many videos in the Project Library, but the playback screen is just not working!
The audio is completely fine, however.
What happened?

Answer 1

Hi
Have no clue - but You might try some of this
When iMovie doesn't work as intended this can be due to a lot of reasons
• iMovie Pref files got corrupted - trash it/they and iMovie makes new and error free one's
• Creating a new User-Account and log into this - forces iMovie to create all pref. files new and error free
• Event or Project got corrupted - try to make a copy and repair
• a codec is used that doesn't work
• problem in iMovie Cache folder - trash Cache.mov and Cache.plist
• version miss match of QuickTime Player / iMovie / iDVD
• preferences are wrong - Repair Preferences
• other hard disk problem - Repair Hard Disk (Disk Util tool - but start Mac from ext HD or DVD)
• External hard disks - MUST BE - Mac OS Extended (hfs) formatted to work with Video
( UNIX/DOS/FAT32/Mac OS Exchange - works for most other things - but not for Video )
• USB-flash-memories do not work
• Net-work connected hard disks - do not work
• iPhoto Library got problems - let iPhoto select another one or repair it. Re-build this first then try to re-start iMovie.
This You do by
_ close iPhoto
_ on start up of iPhoto - Keep {cmd and alt-keys down}
_ now select all five options presented
_ WAIT a long long time
• free space on Start-Up (Mac OS) hard disk to low (<1Gb) - I never go under 25Gb free space for SD-Video (4-5 times more for HD)
• external devices interferes - turn off Mac - disconnect all of them and - Start up again and re-try
• GarageBand fix - start GB - play a few notes - Close it again and now try iMovie
• Screen must be set to million-colors
• Third-party plug-ins doesn't work OK
• Run "Cache Out X", clear out all caches and restarts the Mac
• Let Your Mac be turned on during one night. At about midnight there is a set of maintenance programs that runs and tidying up. This might help
• Turn off Your Mac - and disconnect Mains - for about 20-30 minutes - at least this resets the FireWire port.
• In QuickTime - DivX, 3ivx codec, Flip4Mac, Perian etc - might be problematic - temporarily move them out and re-try
(I deleted the file "3ivxVideoCodec.component" located in Mac HD/Library/Quicktime and this resolved my issue.)
buenrodri wrote
I solved the problem by removing the file: 3ivxVideoCodec.component. after that, up-dated iMovie runs ok.
Last resort: Trash all of iMovie and re-install it
Yours Bengt W