yes, you should easily be able to make a 1:25Pm flight. Ask for "early flight" disembarkation just to be safe. You should be off the ship by 8AM that way. I would book a private limo so you don't have to wait for Carnival's shuttles.
Its about 40 miles from Galveston to Houston Assuming you are on the Conquest, you will be traveling on a weekend Day... it should NOT take a private limo/shuttle 1 and a half hours to get to the airport...
Carnival Cruise Lines:
Fantasy 90, Celebration 95, Victory 05, Conquest 05, Spirit 6/06, Freedom 6/08, Holiday 7/08, Victory 6/09, Valor 9/09, Dream 6/10, Splendor 8/10,Conquest 8/11,Magic 11/11,Triumph 4/12,Spirit 7/12,Freedom 11/12, Triumph 2/13 - The fire cruise
NCL Dream October 2006, RCCL Mariner OTS June 2007