Mitel 3300 changing DHCP servers
 

We are retiring one of our servers and are trying to move the DHCP settings to the new server with no luck. Even exporting the settings then importing them to the new server has not worked.
The handsests (mitel 5212) get as far as showing the correct vlan but don't go as far as connecting to tftp, in the end they keep the IP address from the data side rather than the voice side.
Any ideas?
Hardware:
- mitel 3300 ICP
- mitel 5312 handsets
- server 2003 (about to be retired)
- server 2008 (new server)