Congratulations on your new shiny Mac! There was basically an Intel/PPC compatibility bug for comics with lettering or irregular panels that affected comics created before Comic Life 1.3 was released.
This has however been fixed - so please make sure you have the latest version of Comic Life (1.5.5).
1. Make sure Comic Life is closed.
2. Using Finder, find and holding down the "control" button on your keyboard, select Comic Life.
3. Then click 'Get Info' in the pop-up Finder window and check "Open in Rosetta".
4. Then launch Comic Life and open the comic - it'll open fine (just run a bit slower)
5. This will force Comic Life to use Rosetta and enable you too open the PPC file.
6. Once your file has opened, please use Save As and create a new .comicdoc file with a new name, and quit Comic Life and remove the tick from "Open in Rosetta" (steps 1 - 2)
The above will only work if going from PPC-based Mac's to Intel-based Mac's (OS X 10.6 Snow Leopard and earlier - it doesn't work in later versions of OS X).
Doing this will make the file portable to any other Comic Life 1.5+ version (including your new totally awesome Intel machine).