I also have a GoDaddy account (IMAP) and my wife has had a number of problems with her emails on macs. I brought up this topic with IT at my job and was told that GoDaddy has known "mac" problems and hers are documented and yet unresolved. I'm quite invested in GoDaddy at this point, and can't believe that a national company of its size can't make things work on the mac. Another tale of woe regarding GoDaddy.
Good luck with your problems.