01 Rodeo brake question/problem

When I initially press on the brake, all is fine. As I press harder, there is a kind of creaking noise coming from the pedal (not the abs sounds) and the pedal slowly "clicks" down in small notches as it makes the creaking noise. Not all the way to the floor but in very small increments. I can't detect a loss in the brake pressure via the peddle or in braking power. This happens at all speeds from stop and go traffic to braking when coming off the highway. Happens on smooth and bumpy roads.
I've had the brakes changed at regular intervals and the fluid checks fine (other than the normal fluid "shift" as the brake shoes wear down) The brake pads still look good and their is no grinding or wheel shimmy when I am applying the brakes. The brake light has NOT come on at all during this time (past 6 months, has gotten more frequent lately)
Any ideas?
I am thinking that there may be some air in the lines.

Jason in NYC

Three things come to mind. Air in lines, though this usually just makes the brakes feel mushy. Bad rubber brake lines, between the chassis and calipers/axle (old worn lines can swell under pressure greatly reducing braking). Or, sticking caliper piston.

This could also be something up with the master cylinder (creaking, choppiness), or something binding up above the brake pedal? Just a couple guesses!?!
G/luck
Joel