After your above post, I tried again and sure enough, it worked as expected in Safari, but still not in Chrome. I made a modification to the 'FileName' in the image upload code, as I'm attempting to follow a strict naming convention and tried the upload/overwrite again. Once again, it worked just fine as expected. I then tried a third time and it failed, hanging at the "Please Wait" Animated GIF.
Thinking it may be a problem with that particular image, I tried inserting a new record with that exact same image and it uploaded just fine. Tried then updating THAT record with a new image and succeeded without problem. Tried a second update to exact same record, and failed again as mentioned above.
Which got me thinking, maybe it's something with updating a record for a second time. So I uploaded yet another new record, and attempted an update. But alas, the FIRST attempt at an update failed.
Maybe it's an intermittent server issue, but I run into the same problem on my local XAMPP set up, and it's odd it would only do it on the update, not on the insert.