Hi linbmcd,
My apologies, missing from the instructions above is that you have to hold the Option key in Finder, then click Go and you will see a hidden Library file. This is your User Library. You'll find the iMovie file in the Preferences folder.
In iMovie 10 (2013), I would suggest you start with a new movie, add a few clips from the Maps and Backgrounds content that is part of the program, and then try your transitions again. That way, you can see if the issue is with the software or your media.
This article has some other general troubleshooting guidelines:
Isolating an issue by using another user account
http://support.apple.com/kb/TS4053
The issue at hand may simply be caused by a bad preference setting or user-specific data file.
If an issue doesn't happen when logged in to a new user account, then you know OS X and your installed applications are working as expected.
If you need more help with troubleshooting an issue isolated to a specific user account, you may wish to contact Apple Support. If you work with AppleCare to troubleshoot the issue, be sure to mention any troubleshooting steps you have already performed and the results, and the text of any alert messages you're seeing. You may want to take a screenshot of any alert messages so you can refer to them later.
I hope this information helps ....
Have a great day!
- Judy