Duplicate Name Exists on the Network?

Recently, most of the 40 or so pc's on my network began displaying "A duplicate name exists on the network" upon booting up.  I am 100% sure that no duplicate names do in fact exist.  I am running W2k server w/ DHCP & DNS.  However, WINS is not an installed service, so I don't believe that is the problem.  The most perplexing thing is that no configurations changed before this started.  Most of our functionality is there, but a few of the mapped drives, and viewing network resources are not working.  Any help is greatly appreciated.
jebarrAsked:
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speedytortoiseConnect With a Mentor Commented:
I have seen this problem when a Sonicwall firewall is set to pass netbios over tcp from the LAN to the DMZ or another nonexistant domain.  Disabling this fixed my issue.
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rindiCommented:
Try resetting the leases of your DHCP Server. Something else that could cause this is a PC crashed, and the server hasn't noticed that it has gone. When trying to log back on, the server thinks the pc is online still and will send the "duplicate" message.
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jebarrAuthor Commented:
I will attempt the DHCP release.  However, the PC suggestion seems unlikely, as this is occurring to most of the PC's.  Thank you for your prompt response, by the way.
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jebarrAuthor Commented:
Resetting the DHCP leases didn't resolve the problem (nor did restarting the DC).  Any other ideas?
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rindiCommented:
Sometimes a bad switch or a bad port on a switch can also cause this behaviour, or if a port is set to a certain speed or duplex mode and the connecting network card isn't set the same. Usually you get the least problems if everything is set to "auto".
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Ron MalmsteadInformation Services ManagerCommented:
look in your DNS lists...and make sure there are no duplicate host and PTR records.
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sriwiCommented:
clear all of the dns record and start over a new record, every computer that restart itself will register himself on the dns and dhcp again.
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jebarrAuthor Commented:
I guess I should add that I'm currently in the process of deploying active directory.  Only a few of our PC's are even in directory (though they are using DHCP).  Even the ones not registering with DNS are displaying the error.
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jebarrAuthor Commented:
My God, Speedy, you are a genius.  It never even occurred to me that I had plugged in a sonicwall firewall recently to begin configuring it.  Actually, it seems that the time is probably right.  As I type this, I've removed it from the network, & we'll know Monday if that was the solution (but I'm willing to bet it is).
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jebarrAuthor Commented:
6 days out, & still no problems.  Seems like the Sonicwall was the cause.  Thanks all for your efforts.
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