This just happened to me also. I took the 32mm tires off my wife's Specialized Vita and installed Continental Ultra Sport 28 mm tires and I got lumps on both the front and the rear.
What I did was pump the tire up to 60 lbs and then rolled the tire on the garage floor pressing down on the tire and rim with my weight a few revolutions and checked for the lump which was still there.
Pumped the tire up to 90 lbs and rolled it the same way and then heard a snap sound which must have been the bead seating because I checked the tire right after that sound and the tire was nice and true.
This worked for both the front and rear tires.

Mark