Ping will not resolve

Hello:

I have an XP computer. If I try to ping another host on my network (the
exchange server) it does not reply. All other machines are working fine.
This machine was working fine before today. I have done all the normal
things. I checked for routes, checked the host file, did an arp, nbtstat
and even a "ipconfig /flushdns". I also have shutdown and rebooted the
computer.

Does anyone know what might be going on? Thanks.

Harrison Midkiff