can't open documents from iCloud

This issue isn't new to me, but it's annoying:

I can't open documents stored in iCloud.

It does not depend wether they're pdf, numbers or whatever format.

I guess this is somehow due to my connection (G4 hot spot from iPhone), but I am online and can do whatever I want (web, mail, dropbox, even updating documents in/from iCloud), so the connection works. But I can't open my documents for whatever reason.

Where to look?

Thanks!

david