I have a similar problem to this that causes my initial uploads to all be duplicates. My method used to be "copy album from explorer, paste into album list, then paste into artist list, sorting as necessary". Logicaly, I figured pasting the exact same file twice within the same session would cause it to be uploaded once, but no. I realize the dificulties of detecting duplicates across syncs, but uploading the same path/filename twice in the same session really should qualify as a bug, not a design decision.

Matthew