Why can't I share my Desktop?

My main computer have most of its partitions shared in the network and it acts like the central file storage for all my computers. My Desktop on that computer is shared as well. For some reason I cannot read any files from that desktop though. I cannot open documents, I cannot view images, and I cannot copy files from that folder when I'm on another computer in the network. All other shared folders can be read without problems, and desktops on other machines in my network can also be read.

Any clue?

Right-click on the My Documents folder -> Properties -> Sharing then check what rights the guest user got. May be some other user too that needs updating.