Did you change your internet connection from PPPoE to DHCP at:
1. Log into router 192.168.0.1 or what ever you might have changed it to.
2. Setup > Internet > Manual Internet Connection Setup
3. Under "Internet Connection Type" make sure it is set to Dynamic IP (DHCP).
4. Enable Advanced DNS Service should be Unchecked
5. Host should be blank (Unless ISP tells you otherwise)
6. Unicasting is ok to leave checked. (Unless you know for a fact you don't need it)
7. DNS servers blank (Unless you know what they should be, or you want to use 3rd party)
8. MTU is usually 1500 (Unless ISP says otherwise)
9. MAC can be 0's, or not. Doesn't matter unless your ISP provisions CPE. (They would usually tell you)
10. Save Settings.
I could give more specific instructions, but I need to know:
1. Your ISP.
2. Model number of modem
3. Other routers, switches, servers, etc?