Lost File and printer sharing in Win XP Pro

For about a week, I have lost File and Printer sharing on my Win XP Pro LAN, which has 3 computers, #s1-3. In Network Neighborhood/workgroup of each computer, I can see the other two computers on the LAN.
I do have full access to computer #3 but not to the other two computers.

I can ping from #1 to #3 but not from #1 to #2.
I can ping from #3 to #1 but not from #3 to #2.
I can ping from #3 to both #1 and #2.
So in this respect, #2 is the most problematical.

The 4 port LAN router (DI-604) is not causing a problem with internet connection.

When the software firewall (NetDefense) is shut off, there is no change in the situation.

In the Network Connections/TCP/IP, on the Advanced tab, on computer #2, the message is “Windows cannot display the properties of this network connection. Windows Management Instrumentation (WMI) information might be corrupted. Again, computer #2 looks more problematical than the other two computers.

However, on computers #2 and 3, the Advanced tab is accessible. I can see there that the Win XP Firewall is off.

I have run from the command prompt on all computers the command “nbtstat –n” to show the browser master information (MS Computer Browsing Service). The only odd thing is that on computer #1 (the browser master), the workgroup name appears both as a “group” and as “unique”.

System Restore does not help.

I have considered resetting the ICP/IP on computer #2 but it seems quite risky.

Thanks in advance for your expert help.