They're definitely not VPN phones. There are no VPN settings in the phone. They worked perfectly prior to the upgrade, and now they don't. I've been trying everything today. They definitely are seeing the IPO because it won't let you log the extension in with the wrong password. Here's what monitor spits out when the phone tries to connect:
13:17:08 1018207mS H323Evt: Recv GRQ from 74.106.227.29:49300
13:17:08 1018207mS H323Evt: e_H225_AliasAddress_dialedDigits alias
13:17:08 1018208mS H323Evt: found number <519>
13:17:08 1018260mS H323Evt: Recv: RegistrationRequest 74.106.227.29:49300 on 1; Endpoints registered: 0; Endpoints in registration: 2, tpkt user: 00000000
13:17:08 1018260mS H323Evt: e_H225_AliasAddress_dialedDigits alias
13:17:08 1018260mS H323Evt: found number <519>
13:17:08 1018261mS H323Evt: RRQ --- CallSigProtocol is H323AnnexL_P. Go for Avaya 4600IP phone
13:17:08 1018261mS H323Evt: RRQ --- Register extn 519 using product IP_Phone, version 6.3116, id Concrete Protec_5eeb695409131258
13:17:08 1018261mS H323Evt: <519> registered, ipo behind nat 1, phone behind nat 1
13:17:08 1018262mS H323Evt: RASSRV: GetAlternate GK list returns <none>