Hi Peter,
We ran into this issue, and found a resolution which was not stated here. Thought we would share to assist others. We installed DMX 6.1.6 on DNN 6.2.9, added document exchange to new page. module had blank interface as stated in earlier responses. This was caused by an error with javascript, specifically "ComponentArt_FormSubmitHandler is not defined". This lead us to the following post:
http://www.componentart.c.../forums/t/61265.aspx This lead us to opening the web.config and commenting out the following line
<!-- -->
Saved, pushed, and reloaded page to have everything working properly.
Hope this helps others,
Foremost Media