New users account (net accounts /sync)

When I setup a new User account, it seems the PDC and BDC don’t sync up correctly. Upon completion I use the “net account /sync” command. It looks like this doesn’t work correctly. I don’t get any errors from. But, when I try to give permissions to that user on the BDC folders it says account unkown. I then restart the server and all is good. Why would I have to restart? What could be causing this problem?