I recently moved into a new construction, and the fiberglass shower pops and creaks when standing in the shower. Do problems such as this generally subside over time as the house settles?

The builder suggested that its not a real problem. However, I'm worried that over time cracks will develop in the fiberglass. Is there any measures that can be taken to stop the noisy popping, and is this situation indicative of a greater problem?

This situation is normal, irreversable, and as your builder says not a real problem.

Fiberglass tubs, tub/shower combos and shower bases all move and distort to some degree when filled with water and people are in them.

The result is popping or squeeking sounds where the unit is fastened to wals, comes into contact with floors, or where two pieces of the unit are joined together....and there is no remedy other than to install a different type shower base or tub.

Under normal use this should not result in any damage to the unit.

If you do experience cracking or damage as the result of normal use, the manufacturer and builder's warranties will cover repair and/or replacement.

Just to let you know, I had the same problem. The pops were caused by the drain rubbing against the sub-floor (the hole for the PVC pipe was not centered. I chisled away about 1/8 inch from the sub-floor (where it was rubbing) and the pop disappeared.

I did not realize that pops and creaks were options in new construction. Do all of the other units have the same problem? If not tell the lazy sob to make yours quiet like all the others.

Sometimes this can be caused by the fiberglass floor of the shower not being supported from underneath. A lot of manufacturers recommend putting some plaster under the supports of the shower floor that will harden when it drys to support the floor a little better and curb deflection. This will occur more if you weigh more than 200 lbs. I've heard. Many builders don't bother doing this step but it is recommended. Here is a link regarding this:
Lasco FAQ

Shower pans should not move or squeek! This one is not installed properly and may develope cracks in the pan dependent upon amount of movement. The movement will also stress the pan to tile joint and cause moisture migration over the curb, behind the tile legs and into the wall structure.

I used some "Great Stuff" insulating foam, and it stopped any popping for a few weeks. However, it seems to have stopped completely over time. In my case, I think it went away as the house settled.