screen saver switching screen savers

I set my screen saver to my Flickr account photo stream. It used to work great. Basic idea was that the latest of whatever I uploaded to Flickr would show as my screen saver. Loved it.

Now it will not work for long. It will change to an apple standard screen saver after 2 minutes or so.

So far, I have gone back and again, set it to show my screen saver as Flickr -> photo stream. It will then show for about 15 minutes perhaps. Then returns to a standard apple screen saver, like the national geographic pics.

Any idea why this is happening and how to make it stay on my screen saver of preference on Flickr?

Thanks