I suppose the GoFlex uses uPnP to tell the router to forward it's ports to him. So search in the GoFlex for an uPnP option, and turn it off. You could also disable uPnP on the router, but in that case you'll have to manually forward all needed ports. Some online games doesn't like that.
I turned all the networking services including uPnP off. On my router, all I see is new server under uPnP. I completely removed the GoFlex from the power. It's like Seagate is forwarding port 80 and it won't release. I forwarded port 80 on my router for the new nas drive and it ignores the port, due the GoFlex. I reset my router back factory.. Any ideas?