Think its chickweed??
Is it possible to get a much bigger and closer-up picture of it? Photobucket allows me to upload some pretty big photos.
I can't even tell if those are white flowers, or if my eyes are fooling me, or what the leaves are really shaped like.
Compare what you have with these images.
Here is a link that might be useful: chickweed images
that worked. Don't know why I did not think of that!