To eliminate possible culprits, remove Matrox from your system and try again. 16 GB is not much with 12 cores installed. If you captured, HDV or DV are the only possibilities of the codec in use, and your system is more than capable of handling that.
Is there any way to make this stuff work?
I'm always leery of people who have issues with PP on a machine they didn't build themselves. Most pre-built computers have a lot of crap on them that can easily interfere with the Adobe suite.
I'm even more leery of people who have issues with Premiere Pro while using Matrox.
Here's a recipe for a good editing experience:
1. Know what you're doing with computers.
2. Buy the parts and build your own.
3. Use Windows 7 Pro 64 bit.
4. Install only the programs you need to edit.
5. Test things out before you install any third-party software or hardware.
6. Don't use Matrox.
I can't say the above formula is absolutely guaranteed to work, but it sure goes a loooong way towards eliminating issues.
You should get in touch with Matrox support on this issue--my guess is that either you made errors during the install & setup
of the Matrox unit or it is defective in some way. That machine has more than enough horsepower to provide a good
editing experience. Don't get discouraged--just get in touch with Matrox.