Most routers will default to ch 6, right in the middle of the ch 1-ch11 band. My neighbor's router is on ch 6, so my router would jump to other frequencies, then my computers would have to find it, which after a few minutes it would. This caused problems until I just set my router to a channel other than 6.
Your router has a network name that your computer will look for. For example, it may be "default" or "linksys" or a name of your chosing, "JoesRouter", that you have entered into your router. When you do a "site survey" with your computer you will see, for example, "default" (your neighbor's D-Link), "linksys" (your other neighbor's Linksys), or "JoesRouter" (yours).
You click on "JoesRouter" and click Connect To. Your computer will lock onto that regardless of its frequency.
Perhaps "default" (neighbor 1) and "linksys" (neighbor 2) are both on ch 6, their factory set channel. They don't fight for frequency because they are each too far away to interfere with each other. However you are right in the middle. So, if you allow your router to be on ch 6, it will get interference from both and try to change. So, pick a channel, any channel, as long as it is not ch 6 and hard enter that into your router. This will be done during the setup wizard.
Remember, you should always do your router setup with an ethernet cable, not wirelessly!!! If you screw something up, you can't communicate with your router.
Any user names or passwords, network names, etc you use, make note of.
First get it all working without encryption. When you have it going like that, then go back and set up encryption. Have the manual in hand and make notes as you go... again, hardwired, not wireless when you do this.