Problem with mac mail (imap) not working all of a sudden.

Over the last couple of days, my gmail is not working on my mac or ipad mail. (imap). It works in Gmail. What happens is I get a triangle next to my gmail account but my aol and yahoo accounts work fine in the (imap) mail. When I click on the triangle, it says "Connections to the server “imap.gmail.com” on the default ports timed out". I have tried everything from deleting the email accounts, putting them back in, rebuilding, and synchronizing mail. I have rebooted the computer several times. I am frustrated now as to what the heck is going on. Its driving me nuts. By the way, everything has worked fine for over a year until this past weekend. That's when this all started.