Cannot get my computer to serve a shared folder

I previously had both my Shared documents and another folder, Transfer at the
root directory of my hard disk set up as shared folders. When I start up my
computer, a process says it has a Data Execution fault, and now when I click
on the View Workgroup Computers, it crunches for a while and then says I
don't have permissions to access it. I have rebooted, reset up my network
with the wizard (placing my computer in the "HOME" workgroup). How do I get
the ability back to share my stuff?