I can't seem to map a drive letter in Server 2003

I have two servers who names are Y1 & Y2.  Each is running Server 2003 with the same Service Packs installed.

Everything was working fine, then 2 days ago I started having a problem accessing my servers (2003). I cannot map them using the computername. I can only map using the ip address.
Here is what happens when I use the computername:
      net use i: \\y1\i
      System error 1396 has occurred.
      Logon Failure: The target account name is incorrect.
-but when I ping the name:  ping y1  -I get a response.

I seemed like a DNS issue, so I went to DNS on both of my servers and saw a problem: I have 2 servers, Y1 and Y2.
The DNS on Y2 has a forward and reverse lookup zone, and lists server Y1.
The DNS on Y1 has only a forward lookup zone and lists only itself (Y1). When I try to add Y2, I get the message "Access was denied. Would you like to add it anyway?"  I try to put in Y2 manually. It's there now, but with the message "Cannot contact the DNS server".
I try to put up a reverse lookup zone using the wizzard, but at the "finish" I get an error: "The zone cannot be replicated etc. because the required application directory partition does not exist etc. Only Enterprise Administrators have the appropriate permissions to create it."  Of course I am a Enterprise Administrator, so the message is meaningless.

I tried all the small stuff, like NETDIAG /FIX , IPCONFIG /FLUSHDNS,   I restarted both machines. No dice. Help!    

Two more points:
When I try to force replication in AD Sites and Services (at either server), I get an error: "The target principal name is incorrect"
NSLOOKUP on the server name gives me the ip address of my internet provider.
>nslookup y2.yetedot.biz
DNS request timed out.  timeout was 2 seconds.
*** Can't find server name for address 192.168.10.2: Timed out
Server: dns2.bezeqint.net
Address: 192.115.106.35  

I hope I provided all the information.  Thx a million!!