If you’re using Apple Mail, try dragging documents directly from a DT view to Mail’s Dock icon, creating a new message containing those docs as attachments, or to any message currently being composed.
Whoops - that’s no help for you with Gmail; sorry.
As GMail is a web-based application sending attachments to a new GMail message is not like creating it locally on your Mac. We currently do not support web-based software but only locally installed application such as Apple Mail or Microsoft Entourage.