Beware!!!
I had a problem like that some months ago, it seemed to be caused by some kind on virus/malware which my computer had picked up on our travels.
Sometimes a single click on the back arrow was sufficient, at other times it required two clicks.
I took quite a bit of fiddling with various anti-virus programs before I got rid of it.
As you click on the back button, look at the tool tip text, it should show something about where you expect to go back to, see the attachment.
If I remember correctly, when I had the problem the tool tip said something about "doubleclick".
JimB