Cannot browse after ADSL Disaster

We had our ADSL connection accidentally inactivated by 
our ISP. During that time we were forced to go back to 
using a Dial-up account. At the time, our ADSL router was 
performing Port-Redirection for our mail server, OWA and 
pop3. When we transferred to dial-up, email delivery 
stopped. We run the Secure Mail Server wizard within ISA 
Server which is installed on our server which also runs 
Exchange 2000 for our mail server. This fixed the problem with mail
delivery.

But...
We are now back up again on ADSL and although our Router (DLINK DSL-500)
says we are connected, neither the server or clients can 
browse the internet or send and receive email. 

I have checked DHCP is assigning the IP address of the 
router as the default gateway. we can ping the router, 
ping the server etc from the clients but cannot do 
anything else..

Please someone help. I have tried all i can think of..
Please email me with any suggestions...

Regards,
Belinda

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