Well, since you managed to get in, this will be completely unhelpful, but here goes.
I also have a Mac and suspected compatibility (ie. Gates monopoly) problems, but kittenfemme runs the same OS and browser versions that I do, and she has no problems getting in. She suggested that my security may be set too high. Mine is on the middle setting (accept cookies from sites you visit, but not from advertisers on those sites).
Since I'm not inclined to liberalize that setting, I'll never know if she's right, but if you wanted to take the chance and then report back, I could live vicariously through you.
I was GOING to say that if that didn't work you should try stripping naked, bowing before your machine and praying to the ghost of Steve Jobs.
But I won't.