On SW18 SP5.0, I have a problem with SW's whim with opening SW19 files: - on my machine no problem, the behavior is normal; - on a colleague's machine, it doesn't want to: either it puts a message that SW has encountered a problem or it doesn't do anything, but nothing at all.
Out of 4 machines (1 recent laptop, 2 sister-machines including mine and the last one a little older), all under W7, only mine works. On the others, I have all the behaviors possible.