Still evaluating things.
I've created a 3D model
I imported into Scene Builder (as an ASE from 3DS Max 6)
I've Published using a variety of values for the Broadcast key.

I get nothing but a blank screen, not even a watermark. What am I doing wrong?

You don't need a broadcast key to view content locally. Maybe something went wrong as you were publishing. Try enabling Show MTX Errors in the Load tab of Scene Builder. Drag and drop the mtx you previously created onto Scene Builder and any MTX errors will show up in the Object Info window.

Hi. Same thing happens to me. Nothing but a blank screen. Not even the watermark.. Please, let me know any solution.

That blank screen indicates that something is wrong in your *.mtx code. It is a Syntax problem.

If you strip the *.mtx of all interactors, actions, MTSTimeElems...all but the object and texture declarations, then you may see the scene properly populated. Otherwise, there is something wrong with an object or texture declaration (fix that first if the scene is still blank).
Then, add in your MTSTimeElem, Interactors, etc. in an interative process to determine which scene component has bad syntax. (cut and paste from an earlier version of the scene MTX code...paste, save, view as a test, go to the next component and repeat).

If you have an old version of Internet Explorer, then you might be able to open the *.mtx file in that application. An XML parser will look at the code and tell precisely which line your syntax error is in. If all the code of the scene displays, then your code is correct.

hth
DavidR