Mitel 5312 IP Phone

Could someone please help me out with a phone problem?
I am trying to use a few extra phones that I have in the office for testing of my system. These are Mitel 5312 IP Phones. I have them configured and can get calls to the phones, but can’t talk across the connection. Also the phone will lock up after the call and can’t make any calls out.

I have one 5212 and that phone works great with no problems. I copied the SIP configuration from the 5212 to the 5312 and still no love.

Here are the specs on the phone.

Mitel 5312 IP Phone
S/W R7.

If anyone has any tips on what I need to do that would help greatly.