strange problem: watching videos causes wifi box(AP) reboot

I have a laptop Dell latitude E4310
my system is fedora 16, I'm using firefox
If I watch videos online, like youtube
after tens of seconds or several minutes, the wifi box(AP) will automatically reboot, causing network outage.

the wifi box is SFR neufbox, I'm in france.

if I use other laptops, smartphones, ipad to watch youtube videos,
for most of the time, it is of no problem and the wifi box works fine, but ocassionally the box still reboot

what is wrong with this?
any potential reasons?
thanks