Like Colin said, ANYTHING that pops up a dialog box will cause the Journal script to fail.
I thought the Journal files would be a really cool way to do some timing testing. However, every project we work on uses Worksets, and everyone's favorite dialog box:
"This file has been copied from a Central file, blah, blah,blah, blah, blah, blah,blah, blah, blah, blah,blah, blah, blah, blah,blah, blah, blah, blah,blah, blah"
crashes the script. I found I had to be so specific with ensuring I had already made a Local file that was EXACTLY the same for each test that the process was unusable.
Also, any DWGs or Revit Links that are not found will crash.
And, if anything is different, it'll crash. If you have anything in the Journal that edits an element & that element has been deleted. BOOM