net view and net use commands (or network neighborhood) require a session be established on the target whereas ping does not. Things to check:

• Target must have Server service running to establish session.
• NT target must have licenses available to establish a session. A server overcommitted on its licenses can respond to ping but not a session oriented protocol.
• Net commands require port 139 to be enabled on routers.
• ping send small packets (74 bytes). A router may be misconfigured to only support small packets. Use ping to test packet sizes normally used by Net command:

  ping target -l 1012
  ping target -l 2024
  ping target -l 3036
  ping target -l 4048
  
  

• Verify that target is not hung. Ping has been know to generate responses on hung systems.

C:\WINNT>ping /?

Usage: ping [-t] [-a] [-n count] [-l size] [-f] [-i TTL] [-v TOS]
            [-r count] [-s count] [[-j host-list] | [-k host-list]]
            [-w timeout] destination-list

Options:
    -t             Ping the specified host until stopped.
                   To see statistics and continue - type Control-Break;
                   To stop - type Control-C.
    -a             Resolve addresses to hostnames.
    -n count       Number of echo requests to send.
    -l size        Send buffer size.
    -f             Set Don't Fragment flag in packet.
    -i TTL         Time To Live.
    -v TOS         Type Of Service.
    -r count       Record route for count hops.
    -s count       Timestamp for count hops.
    -j host-list   Loose source route along host-list.
    -k host-list   Strict source route along host-list.
    -w timeout     Timeout in milliseconds to wait for each reply.