We currently have three sites that have 7960 phones deployed at each site. The phones are running firmware version 5.0(4.0), a rather old version. They are using SCCP to register with a CallManager running v3.3. At one specific site the 7960s are randomly dropping calls and the PCs that "piggy-backs" off of the phone shows that the NIC has "limited ot no connectivity". It is like the phone power cycles without actually power cycling. The phones are connected to a 3560-24 PoE running IOS version 12.2(25)SEB2. The other sites are running the exact same hardware and software versions as the "affected" site and they report no issues whatsoever. Voice traffic is in its own VLAN and there are no bandwidth congestion issues or general connectivity problems. We even went as far as taking a 3560 from a "working" site and temporarily installing it at the "affected" site, but the issue continues. We are planning to run a packet sniffer to see waht traffic is tranversing one of the affected phones.
Has anyone experienced anything like this before? Perhaps someone could point me in the right direction as what my next step should be.