Modem + Router connection issues >:(

Hey guys, currently the internet works fine with no problems using just a THOMSON ST5x6v6 SppedToch router. However my problem starts when I try to connect my Gigabyte GN-BR01G router. After conecting the two the internet and network disappears completely (however it'll occasionally connect to the internet for around 3-4 seconds and then drop out again). Yet another thing to add to the list of problems, as soon as I connect the Gigabyte router, it no longer shows up when I search for wireless connectivity with my laptop.

Any ideas guys?

At the moment the current set up is Desktop -> Gigabyte Router WAN port -> SpeedTouch ethernet port

 

are both of the routers wireless? if so then they are probably interfering with each other because they are on the same channel. you can find the channel setting options if you login in to your routers setup screen.