I saw this thread last night and it intrigued me. I'm surprised you didn't get any replies so I'll take a couple guesses and maybe the other guys can elaborate.
One... what might be happening is that the demo's processing settings have been set up differently. Like it has the multi core option selected and all the other fancy stuff I don't understand (Core Parking?). I don't know if these settings effect all projects or can be set up on a per project basis but I'd take a look in the Preferences menus of the Demo and one of your own projects to see if anything is set up differently.
The other thought that comes to mind (and again I don't know because I haven't looked at the demo in quite sometime nor do I know whether this would save CPU power) is maybe the demo audio is MP3 files which are more compact and maybe require less processing.
Whatever it is if your system is spiking out on basic projects it'd probably be worthwhile to contact support to see if they can get things running a little more smoothly.
Which reminds me I have to write up a letter for them myself. Maybe I'll produce a few more projects and write down glitches along the way first though.
Cheers.