Debbie, as Jay said, we need more information. What is the tile set on (eg. green bd., cement bd., etc), was it set in mastic or thin-set (thin-set will be hard like cement, matic will be somewhat flexable). Is the plastic block window flush with the wall? Was the joint between the window and tile caulked or grouted? Are the wall corner joints caulked or grouted. Is your house fail air tight i.e. if you slam the front door with window closed do the walls flex? I'd just about be willing to bet that the window/tile joint was grouted and the window, expanding when heated, is what damaged the tile. Is the window individually set blocks or a prefab nail-on type? By all means insist that the builder fix it; there is no excuse for a job failing that fast.