Hi. Welcome to JA.
I found this on the Sears Tech Help web site.
"You could have a clogged air intake screen or flame arrester that would cause a frequent pilot outage. High ambient temperature (above 115 degrees) could also cause this problem. An insufficient combustion and/or ventilation air supply could also be an issue that would need to be checked. An improper vent system design or improper vent operation could cause a frequent pilot outage as well."
Most likely your problem will be related to the vent system that has been installed. If not done properly then during the right atmospheric conditions a vacuum, or draft can be caused that blows out the pilot light.
The best suggestion I can make would be for you to have the unit looked at by a professional. They will be able to look at the venting and tell you if that is the problem.
Unfortunatly this is a problem that will require hands on by a pro. I cant teach you what you will need to know to determine if this is indeed the problem.