Try this (from Adobe)
Try this;
Solution 2: Change the affinity setting for the Adobe Premiere Elements.exe or Adobe Premiere Pro.exe process to use only one CPU.
To change the affinity setting:
1. Start Premiere Elements or Premiere Pro.
2. Press Ctrl + Alt + Delete and then click Task Manager.
3. Click the Processes tab.
4. Right-click the process Adobe Premiere Elements.exe (or Adobe Premiere Pro.exe), and then choose Set Affinity.
5. Deselect all CPUs except the first CPU listed (CPU 0), and then click OK.
6. Quit the Task Manager.