Ok, this brings up additional questions. Step back a
minute.
You /do/ use DNS for name resolution internally?
If you're using DNS for name resoulution internally, you
MUST use the internal DNS server, and NOT the ISP's DNS
server. That will cause all this to happen, without a
doubt.
Take your LDAP utility out of the equation for now. What
are you trying to do, and what happens when you try to do
it? Are you having problems logging into the domain and
finding resources? Are there any errors in the event log?
I'm not convinced yet that resetting TCP/IP or
reinstalling is needed - do you have any idea if network
settings changed either on your machine or on the DC
since this last worked?