iMovie 10.0.9 won't install on Yosemite for my MacBook Pro

Hi,

My problem began when I was putting together a memorial video for my father who passed away recently. I used iMovie '09 and I kept getting the error that I wasn't authorized to use some of the songs. It prompted me to authorize with iTunes but the popup window had a very old Apple ID. I would overwrite it with my current ID and password and it said I was already authorized. The problem persisted so I bought the songs on the iTunes store. That didn't fix the problem. Then I bought the new version of iMovie. It started to download but paused about 25% into it. Now, when I click on Install in the App store, nothing happens. When I go to Purchases in the App store, it says "Waiting..." with a Pause button. I click on the Pause button and nothing happens.

Any help would be greatly appreciated. I would like to get the video working with the songs and export them so I can share it with my friends and family.

Thanks much,

JT