Please explain this to me, Macs and PCs...

This completely baffles me and I'm hoping someone can explain it. I am moving a site over to new hosting and waiting for it to change over when my husband tells me it that the site is no longer up and he's just getting an index page. He uses a PC. I think that the site has switched over and go to start installing wordpress and putting the site up. Well, on my computer it hasn't switched. I use a Mac.

So I go on to his computer and get the site all setup and I'm still showing the old site on my Mac. It's been a few hours and still the same thing, the new site shows on his PC and the old one on my Mac. I try clearing cache and cookies, I use a new web browser, I use another Mac we have that has never gone to the site, and all still show the old site. After several hours I remove the site from the old hosting account and now on my Mac I get the typical parked domain page when I go to the site but my husband's PC still gets the new site that is working perfectly.

It's like the PC is accessing a different internet than the Macs. I don't know if I can post a link, but if someone on here is working on a Mac and would like to test the site for me to see if it shows up, please PM me. It would be especially useful if someone with a Mac and PC can see if the site is showing up on both computers. Thanks!