I don't know if this problem plagues other Internet Explorer users, but have you ever noticed that you can "disable script debugging" in the Tools->Internet Options->Advanced menu as many times as you want, but it won't stick? Well I found the solution in Microsoft Knowledge Base Article 224926.
To resolve this issue, use the following steps:
1. Open Visual InterDev 6.0.
2. On the Tools menu, click Options.
3. Double-click Debugger to expand the branch, and then click General.
4. Under Script, click to clear the Attach to programs running on this machine check box.
This behavior is by design.