I can't save properly, I can't use effects properly, and I need HELP!!

Question

I've had iMovie HD 6 for a while now. It was quite lovely at first. It did exactly what I wanted it to do, and it did exactly what it was supposed to do. I use it often, and I have quite a few iMovie files saved to a special folder because sometimes I need to edit my movies later on.
For a while now (around eight months or so) I've been struggling with iMovie. iMovie is winning. My first and biggest problem is the fact that my iMovie files won't save properly. All my movies are in the place I want them to be, I save, and then I exit iMovie. The next day I open up the file to work on my movie, and everything is gone except for titles, photos, stillframes, background music and sound effects, and any clips that I edited. I've been dealing this by simply never exiting iMovie while I'm working on a project. iMovie will stay open for days (sometimes weeks) at a time until I finish and can put it onto iDVD and burn it. It burns fine. Another way I've been dealing with it is by editing every single clip in my movie with the effect settings placed so that nothing is actually changed. For instance, I'll use the Hue Adjust effect on every clip, but I won't touch the settings on it so that all the clips look exactly the same as before. This worked well for a while, and it brings me to my second problem...
My second problem is that I can't use my effects properly anymore! Over the months, more and more effects would become unusable. Now I don't have any that work properly. For instance, if I try to use the Fairy Dust effect, I will still have a sparkle going across the clip as I'm supposed to, but the entire clip will be many shades lighter as if I used Brighten and Contrast to make the clip lighter even though I didn't. It is the same for every other effect now. They work, but they make the clip they are used on lighter.
One more problem is that I can't export to Quicktime with Full Quality. If I do full quality, the movie freezes at a single frame partway through the movie while the audio keeps going. I always assumed that this was because the file was too large to work properly, but if I could export my movies with full quality, I would feel better about deleting my iMovie project files. It's always done this. It's not a new thing.
Wow, I have way too many problems with iMovie. Help with any one of them would be greatly appreciated! I really need to do something about this soon. I've tried reinstalling iMovie, but there was no difference. Thank you so much!

Answer 1

It would be a good idea to do close down all programs and do a permissions repair. Use the Utilities/Disk Utility application on your Mac hard drive and follow the on screen directions.
After that, with iMovie closed trash the file com.apple.iMovie.plist file located in User/Library/Preferences. iMovie will create a new file on relaunch.
If you are storing your project on an external hard drive, make sure that your external hard drive is formatted for Apple. Should be Mac OS extended. If you reformat, first remove all of your data on the external drive to another drive, because reformatting will erase all data on the drive.
Update all of your iLife programs to current, particularly Quicktime.
Finally, make sure that you have enough free disk space on your startup drive--at least 10GB, and more is better.
G5