Dont have an answer I too am on Safari with no issues, also use chrome with no issues.
Could be something with your computer, what I dont know, just had my Mac mini serviced, had some other issues, now fine.
I run quite a few Mac's in my home (including a couple iMacs) and have had no issues here.
I do run Firefox on all of them.
Curious ... are there any updates you haven't done on the iMac?
I have experienced issues in the past while collaborating in Final Draft when one of the Macs has not updated.
Maybe? ... just a thought.
Thanks for the responses guys. I usually only use this imac for recording in the barn. I had to bring it in the house because my old Acer laptop that I surf on is just too old now. I don't update this imac because when I used to let it update, it would always mess up my recording software. Firefox seems to be letting me do everything I need to do for now.