Hi,
It may be your freon, a substance (gas) used in the cooling process of your cars a/c system. Freon is also used in refrigerators and home air conditioners. Find a reputable mechanic/shop and go have your freon tested, it shouldn't cost to much and saves a lot of headaches down the road (so to speak). It falls under the category of stuff happens, just make sure you take it to someone that knows their stuff.
Good Luck *!*