This is a fairly generic error at this point. I've found it usually indicates memory issues. Check the Task Manager and see if the tgd.exe process is using anywhere near 2GB of total RAM. If so you're likely running into memory problems. Remember that total memory use must be considered, including Virtual Memory (Vista has a "total commit size" that I think may be accurate). Note in particular that rendering with multiple cores increases memory use over a single thread.
If you are encountering these errors while not rendering, try pausing the 3D preview. If it still occurs it's definitely something to report in more detail.
- Oshyan