We have recently upgraded a customer's routers (3662 in HO, 3620 in branch 1, 1750 in branch 2) to IOS 12.1.5(T10) on recommendation from Cisco TAC.
The voice calls seem to work fine, however I notice that on the branch routers, the "Operational State" goes UP but the "In Status" and "Out Status" show idle instead of seized. On the 3662 I can see the lines also being "seized".
The calls seem to work fine regardless but I am curious why this is so and whether this could lead to problems down the track.