From now on, Gmail blocks "view as HTML" for PDF which have DRM.
I thinks it's new because before you were able to watch all PDF files.
Source :
http://akira.arts.kuleuven.ac.be/andreas/blog/archives/2006/05/gmail-cripples-drmed-pdf-files-view-as-html-functionality.html

No, still works for me.

Tom,
Maybe your browser doesnt let you see the file :/

I didn't test it.
Just look the screenshoot on the page linked in my 1st post.