The 2005 and 2006 models had 265hp and 284ftlbs torque.

The 2007 model has 261 horsepower and 281ftlbs torque.

Any ideas on what happened?

Nope, some new fuel economy measures perhaps. Whatever, nobody can possibly notice 4 hp and 3 ft-lbs. anyway.

Actually, there's a new SAE measurement method that provides different numbers.

That would explain the drop in the horsepower and torque figures for the Pasthfinder and Maxima as well. The Titan has gone from 305hp to 317hp (perhaps tweaking of the engine).

Where did you read or hear about a different SAE methodology being employed?

Google is your friend. Try this query:
new sae horsepower

That was easy...