Polycom and Cisco Voice VLAN DHCP issue

I've been working on this project for my employer for almost 13 hours straight, and it's driving me crazy. We're moving to a hosted IP PBX phone system and we have polycom phones. We also have a Catalyst 2924 and a 2621XM Router.

So, far this is what I know

-We have 3 vlans: 10 and 20 for data and 300 for voice
-The Cisco router is doing the DHCP
-A computer plugged into any vlan port can get the appropriate IP address (e.g., 10.10.x.x for vlan 10; 10.20.x.x for vlan 20)

My problem is that The polycom can only get an IP address IF there is no "switchport voice vlan 300" command on the switch port that it is plugged into. And I see the polycom when I do a "show cdp neighbors." I've also set "ip helper-address" in the VLAN 300 interface on the switch. The thing that gets me completely confused is that the polycom detects what voice vlan it should have (i've seen it pull it up on the phone) but it doesn't get an ip address. It will only get an ip address if there is no "switchport voice vlan xx"

Any help would be so greatly appreciated.

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Do you have a copy of the config for one of the ports.

It should look something like this.

interface FastEthernet0/24
 switchport trunk encapsulation dot1q
 switchport trunk native vlan 10
 switchport mode trunk
 switchport voice vlan 300
 spanning-tree portfast

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