Wireless router problem

Recently, I bought a wireless router for sharing the WiFi signal from my boardband in the house, we done every setting well and could go to internet with wireless singal, BUT, sometimes we couldn't connect internet but the singal was in good condition, I don't know why? Can someone answer me on this what happened? Many Thanks

What kind of router are you using? Whats the brand and model number?

Thanks! It's TP-Link , model No. TL-WR541G, 54M Wireless Router

One of my only suggestions would be to try and upgrade the firmware on both the router and the modem. But....make sure you use Ethernet to upgrade.....if you use wireless...you might ruin the device.

I will try it as per your suggestion. Thanks!