Toyota Repair: Check engine light..., free diagnosis, toyota dealer

Question
I have a 2000 Camry LE-V6 with an automatic transmission.  The car has 43,000 miles.  All scheduled maintenance is done timely and by a Toyota dealer.  In 05/04, the check engine light came on.  I went to an Autzone store for a free diagnosis.  They informed me I had 6 codes shown. The codes were a variety of P0440, P0441, and P0446.  They told me it was a loose gas cap.  They reset the computer.  Three days later the light came on again.  I went back to Autozone.  The same senario occured.  They told me it may take several fill-ups before the light stays off.  After a third trip to Autozone and several fill-ups the light finally went away on its own. The light remained off and I thought the trouble was gone until 09/06/04.  The light came on again.  I went to Autozone.  The used the scan tool.  The same codes appeared.  They suggested it was a loose gas cap again.  I'm 100% sure that I didn't leave my gas cap loose, especially after what I went through in 05/04.  I went to the Toyota dealer and purchased a new gas cap.  I filled the tank and put the new cap on.  The light came on again.  I have had Autozone reset it for a thrid time this month.  Do you have any suggestion of what the problem could be?

Answer
Toyota had issued a service bulletin regarding this condition(TSB EG013-03) it involves replacing the canister closed valve(CCV) it seems to be out of warranty by time, which is three years from date of first use, you may want to check with the toyota dealer if they will cover it since it is a very common problem.