My new tp link router keeps disconnecting frequently..i just bought it yesterday

SOURCE: i have a TP-LINK TL-WR940N

I have the same problem. Some people says that its because of interference from other neighbors' wireless signals or any other in the surrounding etc.You can go to Router Properties and change the CHANNEL to 6 or 11 and observe any changes.

SOURCE: After using TP-Link TL-R480t+ Router Video streaming from internet at sites such as youtube does not work at all

Hi ,This is Clare Su from TP-LINK support technical force.To you issue,I have the following recommendations:1. try to use only one line to connect to the internet,and see if you can watch the video on youtube2.if you can see the video with one line connected to the internet.Then,you can get another internet line with the router.And you can try to set the rule to the website: youtube, let the flow from youtube come in and out just from one wan port.if you can't solve the issue with my recommendation,you can email me. I will help youas soon as possible.My email is:clare.su from tp-link.com

SOURCE: disable Nat TP-LINK TL-WR1043ND

yeap it should be the firewall, here is the manual http://www.tp-link.com/resources/software/201161017075118.pdf
think this should help you.
But if you want my expertise, make the tp-link as a router and vdsl just the internet line. connect it to router wan and buy a switch for all your devices.That should be the safest and smartest way.

Testimonial: "Hi, I've finally found some time to test the dissabling the FW and I can say that in my case it helped. I can see now from TP-LINK IP cameras connected to the VDSL modem/router. Well done guys, thank you for your help. Kvinar"

SOURCE: cant access tp link tlwr340g gui

Unplug the modem network cord from the router, make shure nobody need internet access at the time.

Then access the 192.168.1.1, and it should be the router.
In the Router GUI, change it's address to somethign else.
(192.168.1.X) where X= something between 2 and 254)

Save settings and plug the modem back into the router.