Copy the project to your mac's Hard disk and then run it.
Trying to run any project from a CD or DVD can more easily cause issues.
To find out more info about your mac, got to the blue apple icon (top right of screen),
click it, and select *about this mac*
This window will tell you your OS version, the speed of your mac and how much ram you have.
The nature of Hard drives etc means that when running audio or video it's always better to run the Operating system and program (logic) from the internal HD and if possible use an external drive (much preferably firewire) to run samples or projects from.
For the time being though, copy the project from DVD to your HD. That should make a dramatic difference!
Also, you can check your buffer I/O
Christian wrote some advice about it in this thread: