DNS lookup failure! PLEASE HELP!!!?

Hey guys... I need expert advice. I am getting DNS lookup failure in Chrome and cannot seem to figure out why this is happening. I am in IT so your answer can be technical. I have tried another router which worked fine for a while and then it started happening again. I even tried using google's DNS server but that does not help. I have disabled "network action prediction" and "use a web service to help resolve navigation errors" in Chrome and no luck. I know for a fact that I do have internet connection cause I can ping sites. Could this be due to a network attack of some sort? Like a flooder cause my roommate is also on the network and I am beginning to get suspicious about him? Or could this be a ISP issue? Are there any software I can try and use to detect the problem and prevent it? Please any suggestions will help! Thanking you in advance!