Q: "Document can't be downloaded."

I can "see" documents in iCloud but can neither open them in Pages ('09) nor download them.  I get the following message: "Document can't be downloaded. Please try again."  I am using 10.8.3 on a Macbook Air, and some of the documents were created on a Mac Pro.

I have tried going to System Preferences and unticking/re-ticking Documents and Data (and I have done so with a restart in between, as well).

Any ideas?