What do you do when a program won't open?

I went and upgraded to Leopard and iLife08, and now I can't get iMovie to open. I tried reinstalling but that didn't do it. I don't know much about Mac troubleshooting, so I'm kind of at a loss here.

You can use the Console application in the Applications/Utilities folder to view logs. Perhaps that will give a hint.

You can try repairing permissions via Disk Utility application.

Do you get any message when iMovie doesn't open?

do you have any iMovie plugins that may be preventing it to opening. Maby you can try reinstalling leopard then installing iLife again.

This is the first time I've ever tried to use it. I've never installed any plugins. The error is just that the program unexpectedly quit.

I ran the software update, and it had an update for iMovie. After installing the update, it ran fine.