I have a new CME 4.0.0(1) install with only one 7961 (load TERM41.7-0-3-0S). Since the install, I've had two anamolies with the 7961 (with two 7914 side cars).
1) No dial tone if the handset is lifted or "speaker" button hit- user would have to hit "new call" or "answer". Phone reset and problem cured.
2) Phone was configured and showed three lines (standard call hunting config). If line 1 was busy, call would roll to line 2. However, if line two was busy, it would roll to whatever coverage was designated for line three BUT NOT ring line 3. Phone reset and problem cured.
I'm tempted to replace the phone but want to make sure that there isn't any bugs with CME 4.0.0(1) or the phone load that someone has run into. Unfortunately, it is my only 7961 in the install.
It looks like you are hitting this Bug CSCsc99161 :(
Rarely a 7970 IP phone will get into a state where the speaker, headset, handset, or line buttons will not work to take the phone offhook. In this state the only way to go offhook will be to use the softkeys.
This has been seen in various Skinny phone loads up to and including 7.0(2)SR1. It is not dependant on CallManager version.
A simple IP phone reset will recover the phone.
Further Problem Description:
This problem can occur on Cisco IP Phone 7906/7911/7941/7961/7970/7971 independent of phone protocol (SCCP, SIP) and CallManager version.
Firmware 8.0(4)SR1 or later can resolve this problem.
Hope this helps!