mine works fine in duel band if you are not using the 5Ghz then turn it off no point broadcasting it and saves energy. there are not many devices that are using 5Ghz (apple do) you can buy wireless...

also have a read of this from tp-link Why can not I access the Internet after connecting the TP-LINK router to my modem http://goo.gl/hQTGm

its a known issue with 5Ghz the further you are away and more walls /objects etc to penetrate it is not that strong as the 2Ghz will be. have a read here How to improve the signal strength of my 5GHz...

have you updated to the latest firmware? ahh i see you have well since i updated i have no wireless problems with the apple products using the 2.4Ghz i had a play with the wireless channels and found...

here is a link to the Version 3.0.4 http://files.metageek.net/downloads/BetaSoftware/inSSIDer-installer-3.0.4.37.msi

yep im with you on that you see people buy apple product because they think its the ultimate gear but it has problems just like any hardware/software can have in any device, i am in a shared house...