My network consists for two Win 7 Pro laptops, several Win XP Pro laptops and a NAS backup drive.  One of the Win 7 laptops can map drives to the NAS drive and all the other computers.  One of the Win 7 computers can only see the other Win 7 computer.  At one time the machine could map to all the computers and NAS drive but now it cannot.  I have disabled the MS firewall but it still does not work.  The laptop can successfully Ping all the machines.  I tried mapping using the device shared name and I also tried the IP address but neither work.

Its very frustrating because it worked, then stopped and I don't know of anything that could have changed!