Check your drivers, I doubt this would be the problem since it can see other wifi access points nearby, but it is a possibility. Is the router yours? Or is it owned by someone else, because they may have blacklisted your laptop from the router, which would make it invisible to your PC. If the router is yours, check to see if your laptop's MAC address is being denied access to the router.
I don't think you can make a network invisible to a laptop FROM the laptop, you can just forget it, or disconnect from it. I could be wrong though, but I don't think so. It sounds more like something from the router's end.