Dave:

We had the same problem and realized the pilot was going out when our HVAC gas heaters kicked on. We believe it's a safety feature - if the fireplace logs aren't getting sufficient gas flow, the pilot shuts off. We had the gas company install a larger meter, allowing a greater feed of gas to the house, and haven't had an issue since. Don't know if it will work for you, but you might try calling your natural gas company for a recommendation.

S Frye

It might be a draft issue?

Here is a link that might be useful: chimney liners

Dave -

I've been encountering the same issue with my DVL GSR. How did you correct yours? Someone suggested that it might be a draft restrictor issue - too much draft causes the pilot to go out.

Thanks!