Question: Whats the best way to have file attachments in blocks like you can with nodes? Is this possible with an existing module?

Answer: 
You should start Glassfish with the debug instead of the run option inside the Servers view.
Same problem that you and it was driving me crazy.
My configuration is eclipse indigo over windows 7 and glassfish 3.1.1. The jdk I'm using is 1.7x64. I downloaded the glassfish server tools through the new server window.

I have solved it (it currently works, who knows what's happening in the near future) downloading and installing jdk1.6.30. I haven't uninstalled jdk1.7, but I've configured my eclipse project to use jdk1.6 instead.