Conflicting distribution - Q

I've created a USB boot drive from the 6.7.1 DVD and installed various things since then. After doing sudo apt-get update which I'm not sure why I do from the terminal rather than software sources or other Gui, I get the following error messages at the end of the run. Not a big deal, since not aware that this is effecting anything, but curious, how would I resolve the conflict?

Reading package lists... Done
W: Conflicting distribution: http://packages.x2go.org stable Release (expected stable but got squeeze)
W: Conflicting distribution: http://packages.x2go.org testing Release (expected testing but got wheezy)
W: Conflicting distribution: http://packages.x2go.org unstable Release (expected unstable but got sid)