Have you tried any of the suggestions in the General Troubleshooting thread yet? Very important - make sure you've only got compatible plug-ins installed.
That's really very borderline for PT8, especially if you're using VI's of any sort. I'd strongly recommend more RAM - 2GB minimum, 4GB would be better.
What are the error numbers in the messages you're getting? How is that G-Drive connected - via FW400 or 800?