PDF's are saving with a lock icon. HELP

Me and one of my coworkers often work on a network (I am a graphic designer).  When I save a file as a PDF (to be sent to a customer) on my PC, it is saving with a little lock icon next to it, and she can NOT see the file. Not just in illustrator.  It is not showing in the file explorer either. No, I am NOT saying that she can't open it; she cant SEE IT.  (I emphasise this because I tried google-ing the problem, and there are 1 million post about not being able to open a file, but none about not being able to SEE a file). 

When I go to save the file, I keep it on illustrator default (but I HAE tried the other presets to no avail).  Nothing is checked in the security settings.  HELP ME. Why is it saving like this, and how do I change it? Oh, and it isnt every file.  old files can be seen just fine. it is only files that have been saved in the last 2-3 months.