Fireplaces, Heating Stoves, Flues and Chimneys - Gas Logs Flaming Out

I have a set of vent-free gas logs installed in a "normal" fireplace. They are about 3 years old. I moved in to my house a year ago. The logs worked fine last winter, and I assume fine for the previous owner the two prior years.

This winter, when I light the logs they burn for a short period of time (sometimes less than a minute, other times several minutes) and then they go out. I then have to relight the pilot.

EDIT: To clarify, the pilot is working fine. It stays on fine when the fireplace is not in use.

If I take the logs out, light the pilot, and turn on the burner, the fireplace works fine (at least for the first hour).

What can be causing this? What are possible fixes?

Take a short piece of tubing and blow out the area adjacent to the thermocouple. I have dogs, and their hair will sometimes settle in that area causing a similar problem. Once it is cleared, relight the pilot and see if that helps. It won't hurt to blow out all the orifices, as dust inhibits the gas' ability to come out.

An update:

I left the burner, with no logs, burn for three hours.
Then, I turned off the burner and the pilot stayed lit.
I placed the logs in the fireplace and started the burner.
The gas cut off after less than one minute.

The fireplace does not like the logs this year.

This log set up . Does it have a oxygen depletion sensor on it????? Could that be it.

This log set up . Does it have a oxygen depletion sensor on it????? Could that be it.

according to the manual it does.

if that's it, what are options to fix?
do i need a new sensor, or do i need to clean something, or ???

according to the manual it does.

if that's it, what are options to fix?
do i need a new sensor, or do i need to clean something, or ???

I'll give a quick answer until the OP can come in. The oxygen depletion sensor is simply the pilot and thermocouple mounted such that low levels of oxygen will reduce the flame and turn off the gas valve. Your pilot flame should be about 2 inches long with the thermocouple tip slightly embedded into a blue flame. Anything that reduces the length of the flame will turn off the gas. Check this and also check again with the burner on.

My recent adventure left me with few options but replace the log set. It was old and ulgy with the old style blue flames. The new set was well worth the cost.