Improvement on previous Answer:
Well i do partially agree with @Divin3 only a slight glitch i found was: All new routers are fully backward compatible with older devices hence a router built on Wireless-N will be fully compatabile with device capable of receiving only Wireless-G or older version. Difference will be that while serving to a device with W-G the router built on W-N will go only be able to serve it at the max bandwidth which is device W-G is capable of receiving. Read more details on a device manufacturer support site here
My Addon to the Previous Answer:
Now lets back on the question, my very own personal experience has been bit different in this case. Sometimes older devices aren't able to scan WiFi networks setup with newer security methods. I noticed this when i switched one of my router's security from WEP to WPA2. Few older devices which earlier used to stay latched to the same router, actually stopped identifying it.
So a little bit of workaround could help people facing issues related to this.