I am having this same issue and I've had no luck resolving it.
- 'Automatically detect settings' is unchecked.
- 'Use automatic configuration script' is unchecked.
- 'Use a proxy server for your LAN' is unchecked.
- I have deleted temp internet files, cookies and history.
- The error seems to occur when the web page takes longer than a few seconds to load - almost as though it is timing out.
- Running without add-ons does not solve the problem.
- Upgrading from IE7 to IE8 did not solve the problem. (I was desperate :))
- All other browsers are fine.
- When I run IE as another user on my machine, the issue does not occur.
Any new ideas would be much appreciated.