I have the same symptoms as you describe. I'm using Windows 2003 and have .NET 2.0 installed. However, I'm struggling to fix it. I've tried the following
Replace this line tag_a.asp (and other tag files)
<!-- #include file = "../include_Security.asp" -->
With
<!-- #include virtual = "/CuteEditorASP/CuteEditor_File/Dialogs/include_Security.asp" -->
But I still get the javascript error? Notice that I've changed the include from a file to a virtual. I didn't think you could start an include file with a forward slash?