The only thing that would really make any sense, is that Photoshop Elements has some kind of Safari Extension installed or is attempting to use the Safari rendering engine for something.

Since you've ruled out the easy and pragmatic solutions, you get to go mucking about looking for the ties between the two programs, but based on a very cursory google search, it looks like this has been an ongoing issue for the past 3-4 years, so if it hasn't been worked out by now, I wouldn't go getting my hopes up of it ever being worked out.