I have heard of similar issues before from some of my friends. They were facing issues with accessing their websites through Mac and it was apparently an IP issue. It wasn't a hard one to solve. It took a few Google searches and after a couple of articles by
potatoes we were able to understand how to get a dedicated IP for their domain. On top of that they even realized that there were better hosting services than the ones they already had. Pretty much they ended up changing provider as they were going to save 40 % on the new plan. Pretty impressive!
Go away spammer!
~ Kscherer