I posted in another message that I was on the phone with Apple Support for 2-1/2 hours about this! The first tech put me through every trouble-shooting procedure possible:
- Delete cookies, history, caches
- Delete startup applications
- start Safari in safe mode
- reboot MacBook in safe mode
- Create a Test User and run through all those tests again.
Nothing worked, which didn't surprise me -- the behavior suggests to me that it's a bug in the latest Safari update.
I was then upgraded to a senior tech advisor, who believed everything I said, and we ran a system report which we uploaded (that took most of the call time) which will be submitted to the Apple engineers to see if they can spot anything in the code causing the problem. Hopefully that will lead to a fix in the next update.
In a followup call from Apple, I told the tech that I had read several more reports about the same problem here in the Dropbox community, which he added to the report to the engineers, hopefully as confirmation of the bug.
So I'll first suggest this: Call Apple Support, simply tell them about the problem and that there have been many reports about it, including my case. If Apple is flooded with calls, it will become a "known issue", which might help speed up the fix.
Meanwhile, I have found a helpful and SIMPLE workaround, so you may not have to resort to switching to Chrome as the browser!:
In every case I've found -- my Gmail account, my AOL.com account, and on Dropbox.com -- you can simply drag-and-drop your file onto the upload or attach button!
Hope this helps!
