Help!! Ok...I'm having the same problem before and after the SP1 install. Take off out of SEA, FMC loaded with ZFW of about 121.0...Used TOGA...Gear up, Flaps up...showing normal Climb N1 with Autothrottles engaged. Empty Center Tank fuel to keep the weight down.....but the plane is acting like it's barely single-engine...barely making Flaps Uop speed in level flight.Any ideas???Thank you so much!!!Ed

A screenshot showing your MCP and displays would be very helpfull.Fred.

I agree a screenshot would be helpful -- just a few more ideas: Speedbrake down? What is your OAT (outside air temperature) and altitude?---Martin Boehme

I think the air temp is the likely culprit - if it's out of the ordinary - reset your weather program