I seem to be able to add attachments now. I think the problem was I was trying it out here in this subforum and apparently this area doesn't support attachments (or I don't have permission to post attachments in this area). So I made a post in the forum test posting area (which does support them)
However I can't actually view the attachments on a post (actually, it doesn't even indicate there is an attachment).
Here is an example of a test post I made with an attachment: http://www.avsforum.com/avs-vb/showthread.php?t=1284418
As you can see if you view it in a browser, there is a pic attached. If you view it in the app, there's nothing (I am using the 1.0.3 build).
One more question: any plans to add an "install to SD" option to the app?