I had problems over a couple of weeks with the exact same problem  .... it had never had happened before.   I had to change my browser from Mozilla to Internet Explorer as I could only download on Explorer ..... and it was a real nuisance and time consuming.

However, about a week ago, I realised it only happened when I 'double clicked' on the 'Browse' button.   I now make sure I only CLICK ONCE.

I know it sounds like a really simple thing ....but I'm back to downloading as before without a problem. 

Try it ..... I hope it works for you  🙂