Try this, might or might not work depending on the issue.
Turn off your wifi.
Go to your network preference, click on advance, the you will see the name of your network (router's name), delete that.
Now try to detect it again with your MB's wifi. You have to re enter your password if you have one.
See if that solves your problem.
How about this.
Get into your router's settings.
Under Clients start taking off who's logged in to the router (your macbook and the ones you don't know)
On the wireless section of it, try ot change the channel. It's usually set at channel 7 or 6 depending on who makes your wireless router.
Try every channel until you get a connection.
See if that works.