Try a 30-30-30 reset. My WR841N was having wireless connection issues right out of box, factory reset and firmware update didn't help, but a 30-30-30 reset solved all problems. If nothing helps, you can always try a DD-WRT firmware. I've had several DD-WRT builds flashed on my WR841N, most of them are very stable. Converting to A DD-WRT firmware takes only 5 minutes, and you can always flash back and forth between DD-WRT and TP-link official firmware.

whats a 30-30-30 reset?
how do i apply it?

hadar wrote

whats a 30-30-30 reset?
how do i apply it?

Very easy and takes only a couple of minutes:
http://compnetworking.about.com/b/2009/03/11/the-30-30-30-hard-reset-rule-for-routers.htm

What's the difference between the 30-30-30 reset and hardware reset essentially?
In fact, the hardware reset is the same as factory default configuration.
You just need to press the reset button until all the indicate lights on. And then you can remove your hand.