Hey, my solutions was the .axd mapping.
I have my DNN install pointing to a virtual directory (which points to my DNN install).
I went to the default website properites and checked the .dll mapping and the .axd extesion was in there and mapped to the .NET 2.0 Aspnet_isapi.dll file.
But when I went to my virutal directory and went to properties . . there was no .axd mapping ??
I then added the .axd mapping and . . stopped and restarted IIS . . recycled the application pool and it worked.
No more Javascript errors.
SOOOO . . check your virtual directories and/or separate applications for .dll mapping.
This got mine working.