What Pool, what OS, what CPU, and what temperatures? Mine runs 24/7 without problems.
I'm mining with win7 64bit, i7 3970k, temps are ok (60°), on nexusminingpool.
edit: i've just tried with cestballot pool, and it's working

thanks for your help!
Strange. nexusminingpool gets anywhere from 300-1000 connections and I've not heard of anyone else having trouble before. What error do you get? Is there anything in debug.log?