I have some 7941 IP Phones wich are connected to 3560 PoE switches (version 12.2), the phones were working just fine and suddenly they showed a message "registering..." I found out that the IP Phone had an IP address from the data vlan instead of the voice vlan although port configuration didn't change and it was correct, besides of checking the configuration I connected a 7911 IP phone to that port and it had no problem. What I did was configure that port to belong only to the voice vlan, the IP Phone registered perfectly, then I had to change the configuration back in order to have access to the data vlan from the PC. It happened only with this model. what I need to know is the cause of this behavior in order to avoid this happen again. I took a look at cisco.com and i found a similar case but with 7935, the tac collection sollution was K19769373.
I hope you can help me to find out the root cause and the solution. Thank you in advance.