I can think of a few reasons.
1. Permissions issues with roms or images
2. Emulator settings need to be changed... wrong paths, etc
3. Bad romset for the emulator
4. In the case of images, perhaps the images are not named the same as roms whatever.png should match whatever.zip
First, I would try to launch some roms directly in your emulator, outside of AM. If that works then likely its a paths or permissions issue.
You can post your emulator settings here if you'd like. I have a copy of AM installed on one of my Macs, so I've got an idea of what they should look like.