new Pentax K-5

Hello all,

I just bought a new Pentax K-5 and made some test-shots(under bad light conditions actually) and I noticed that in every photograph I made you can always see a little greenish dot, about 6-8px large.

It's always at around x=3703, y=1496.

What could it be?

Thanks in advance.

PS: I'll do some test shots tomorrow and upload some to show you what I mean.