Disco from steam while hosting

[Seyou]

Hi all,

sorry,maybe somebody else wrote already about this issue but I can't find the post.
Anyway, since last weeks, while I'm hosting with firends,4-5 players..after a while(random..after 10 mins, or after 20 mins..then ok for 1 hour etc etc) it come a steam box saying I've lost the connection...and the most crazy thing is that my router lights(adsl signal and Inatrnet connection) are going off..then after 2-3 mins everything restart properly..apart that I have to relaunch the game.
My net provider already checked my connection and they says its fine, plus it happens only with COD

Anyone experienced something similar or have any idea for hlep?

Thank you all

S!