Eureka!!! I have found it!!! Stop the presses!!!
There is nothing wrong with your flash disk or unetbootin you are using. When I used unetbootin to put Linux Mint on the disk, it re-acted the same as yours - unetbootin paused at extraction of file # 262. What I did was walk away from it and let it run for about a half hour. When I looked at it again, it had finished and was ready to use.
Here are a couple of screenshots, the first one shows just like yours did:
This is the one that 'paused' at file #262.
So after walking away from it for about 30 minutes, I came back and saw this:
My conclusion is that unetbootin is set up to do exactly what it did - 'pause' at file #262. Why it does that I don't have a clue.
So now we will be able to get by this hurdle and move on.
They say that 'Patience is a virtue'; I think that dealing with computers it is a 'necessity'!!!
Onward and upward Harald. There is light at the end of the tunnel - I can see it in the distance.
I think it's safe to say that for all our problems - we can blame Bill Gates and his money making machine called Microsoft.
See you tomorrow.
Oh yes, one more thing, by your own admission you are impatient. Not to get down on you; I am known for being impatient around those who know me best.