I can no longer share files

Hello,

I have my desktop and laptop connected over wifi. I have previously had no
problem transferring files either way between the two machines, and browsing
either machine from the other. But suddenly, I can no longer transfer files
from my laptop to desktop by browsing from the desktop to the laptop shared
folder to copy the file. I get the error message "I can no longer share
files on network make sure the disk is not full or write-protected". I can
still command the transfer from the laptop however.

The disk is not full, nor write-protected. I have redone the network set up
wizard. I have set the folder on the laptop to be shared, and allow network
users to change files. I have tried changing firewall settings.

Anybody know what has suddenly stopped this working?