I ran into this problem this morning. I checked to make sure I had edited admin/includes/functions/general.php in step 4 and found I had missed it somehow. error went away.
I was just working with v2.5 and had the cursor stuck problem where when you mess with the order fields things freeze up in IE (firefox works fine). I added this bit of code suggested by melhaa. seems to do the job :thumbsup: