I see some entries on this but am afraid I don't understand them. I just switched to a new hosting co. and while Firefox loads the WP Edit Page rapidly, Safari no longer does, though I usually use it and it has an automatic signin. I have an iMac and 10.8.5. I cleared the cache files but no effect. The blue loading light gets about 1/3 of the way across the URL, then just stops.
Also, I've gotten a few "can't load something," such as a graphic, and then have to close Safari and start all over again; then it works.