Like so often happens, people forget to tell what they edit with what settings and so did you. You did try to give the hardware facts, and that is commendable.
But it makes a huge difference whether your source material is RED 4K, AVCHD or DV and you did not tell us.
However, a MBP does not even meet minimum practical requirements, so if you do any editing with a more complex codec than DV, then the behaviour you describe is to be expected. Keep in mind that the official Adobe requirements are only meant for the capability to install the software, not use it. See Adobe Forums: System requirements for CS5
Read Bill Hunt on a file type as WRAPPER http://forums.adobe.com/thread/440037
What is a CODEC... a Primer http://forums.adobe.com/thread/546811
What CODEC is INSIDE that file? http://forums.adobe.com/thread/440037
Report back with the codec details of your file, use the programs below... a screen shot works well to SHOW people what you are doing
For Mac http://mediainfo.massanti.com/
Once you know exactly what it is you are editing, report back with that information... and your project setting, and if there is a red line above the video in the timeline, which indicates a mismatch between video and project
Big thanks to everyone who took the time to reply.
I ended up enabling the Root User account, logging on and opening the program, which ran without a problem. I then logged back on as myself and Prem Pro is now running very smoothly.
Now I just have to upgrade the user's skill level (made much easier now that it is working ok).