Las Vegas Home Warranty

I have a new home in Las Vegas Nevada, acquired in December 2008, it now has 4 or 5 cracks in the ceiling all in the same room (great room), each is about 5 feet long. I talked to warrenty department and they advised that I wait closer to the end of the guarantee period has been repaired for two reasons:
1. leave the house for a summer as hot as could occur
Two. They do it once during the warranty period.

Recommendations please (thank you)

Check your warranty.
They should be corrected under the warranty period. If they do not get it right the first time or longer occurs, they must always be held accountable. Many builders in Las Vegas built quickly during the boom and now have many new sources of future income to pay for repairs.
They may simply be stalling.

December 2008 was only a few months ago. Unless there was a large recent earthquakes, it sounds like a problem. You can look in your attic and crawl space in the cracks.

Talk with your neighbors. Do any of them have identical or similar problems. It could be a sign of design, materials or construction defect.