DNS and IP mapping problem. You will be stumped, I guarantee it!?

I host a website through Host Gator. Recently I went to add on a new domain name. When I did so, my primary domain name became inaccessible from the PC I used to add on the new domain with. My other devices, on the same network, were able to display the website just fine however. I flushed the DNS, I cleared the cache, I renewed the IP- I did everything under the sun yet with no results. Does anyone have a work around to this problem?