Here is a weird one for ya! I don't think its a DNS problem... I'm thinking more along the lines of a Netbios problem.

Windows 2000 Domain in Mixed mode.
Windows 2000 DNS server

Problem: Can't connect to an NT 4.0 File Server Share from Windows 2000 or Windows XP Pro workstations.
Note: NT 4.0... I know what you're going to say... but its not up to me! Its not my network, just trying to help resolve the problem.

Say the domain is "domain.com"

The NT 4.0 File server host name is "fileserver"

When trying to map a drive (2000 or XP pro clients) to a share, it can't find the share.

C:\>net use l: \\fileserver\share
System error 53 has occurred.

The network path was not found.
But, using the full host name (with dns suffix) it works.

C:\>net use l: \\fileserver.domain.com\share
The command completed successfully.
Pinging the host name is fine...

C:\>ping fileserver

Pinging fileserver.domain.com [192.168.1.10] with 32 bytes of data:

Reply from 192.168.1.10: bytes=32 time<10ms TTL=126
Reply from 192.168.1.10: bytes=32 time<10ms TTL=126
Reply from 192.168.1.10: bytes=32 time<10ms TTL=126

Ping statistics for 192.168.1.10:
Packets: Sent = 3, Received = 3, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 0ms, Maximum = 0ms, Average = 0ms
Same thing with pinging the full host name.

C:\>ping fileserver.domain.com

Pinging fileserver.domain.com [192.168.1.10] with 32 bytes of data:

Reply from 192.168.1.10: bytes=32 time=78ms TTL=126
Reply from 192.168.1.10: bytes=32 time<10ms TTL=126
Reply from 192.168.1.10: bytes=32 time<10ms TTL=126
Reply from 192.168.1.10: bytes=32 time<10ms TTL=126

Ping statistics for 192.168.1.10:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 0ms, Maximum = 78ms, Average = 19ms
Can anyone think of what could cause this?

nslookup can find both fileserver or fileserver.domain.com