I second Cleopatra''s experiences. Mac''s Safari is not fully compatible with the software they use on PS, so we downloaded Firefox to bypass this problem.
As you can see by the fact that I''m posting here now, using Firefox on Mac works.
Just wanted to chime in here, Safari and PS don''t mix well! Definitely try Firefox, actually Camino might be a great option for you too. Its by Mozilla (the makers of Firefox) but optimized for your Mac. I believe they are still in beta for Camino, but honestly, it is great, I run into very few problems and its pretty fast!