HTML Document Must Exist error

Ive suddenly started not being able to run my app in debug…
A window with an HTMLViewer on it generates an HTMLViewer exception on the .SHOWMODAL line
This is before the HTMLViewer has been asked to do anything in code… the lines in which it is told to loadurl are never reached before the exception.
I cannot understand what the error is, or how to fix it.

Any ideas?

Any further details here?
Please show the code for window.Showmodal

I dont understand.
Thats it.

mywindow.showmodal

On that line I get an exception. No code can be stepped into, its immediate.

Is it an implictinstance (= true) window?

No.

My undhandled exception logs this as the error text:

_WebOLEContainer.ExecuteJavaScript%%o<_WebOLEContainer>s
But I dont have any javascript in play to my knowledge

I was using Rubberviews.
Removed it completely from that window and all is working now.
A puzzle.