Hi:
I had the same problem. I read that the problem may occur when trying to synchronize the default library (Documents). I created a new library (at the same level) and I was able to add it to the Workplace, and see the content of the library.
But... now that I completed that step... I am still unable to download/ upload files! See here: community.office365.com/.../80521.aspx
I'm afraid my answer comes too late for you... I hoped you solved your problem in the meanwhile... and... if you have any comments that could help me... well, I'd be very grateful!