msxml3.dll: The system cannot locate the resource specified

I recently started getting this error in my Ajax application:

msxml3.dll: The system cannot locate the resource specified

This forum lists a number of possibilities. In my case, I was always using a GET request. As soon as my request got too big (i.e. more than 255 characters), I would get this error.

So, I started using POST instead.

But that caused me another problem, which I describe in another post.