I have had these kind of things turn up in my photos before.
i48.tinypic.com...
i48.tinypic.com...
I had the idea that they were something caused by the flash and the damp air (it was raining on and off the night these were taken). My ex boyfriend
insisted they were 'spirits' though.
They also looks similar to something seen in the Capturing the Light DVD (Thread about it here:
www.abovetopsecret.com...).
At one point when a woman is being interviewed, a moving and flashing light can be seen in the background outside of a window. They slow the footage
down and also point out a small, transparent circle like the one in your photo and these. It moves around the screen for a moment before disappearing.
Of course the authenticity of the DVD is up for discussion. But it does look similar. =)