I just created t4's for 17 employees using 2016.2, printing to cutepdf - no problem

I just did a couple more clients and always the same thing. As soon as I hit the ok button on the T4 summary it does create my PDF file, but Sage stops responding.

I am not filing electronically

so I get to the t4 summary, at this point cutepdf prompts me as to where to save the T4 slips pdf
and I click print, cutepdf prompts me to save the summary pdf
which takes you back to the print records summary, and I click ok, back to the sage home screen

It's not the electronic filing part that causes Simply to stop, it's when I print the T4's and summary. I go through the same process as you did above. It does print T4's & summary to a PDF file but it's as soon as it finishes printing that it freezes. It doesn't prevent me from doing the print and filing...but having to always restart the program is very annoying.

The program may be displaying a dialog box offscreen with an 'OK' button on it - possibly in a location where the second monitor used to be.

Sometimes alt-spacebar, M  (move) will let you move it with the arrow keys or the mouse, back to where you can get at it.

no other dialog box that I can see. Right after I print the T4 summary I get the little circle that turns round and round and round until I get the message that the program has stopped responding. Then I select stop the program as if I hit the wait for the program to respond, it never does. Don't know if it's my PDF printing program causing this issue or as it happens with both my 2015.4 version and my 2016.2. Maybe I'll try a sample company and print once to my printer to see if it does it again.

no other dialog box that I can see. Right after I print the T4 summary I get the little circle that turns round and round and round until I get the message that the program has stopped responding. Then I select stop the program as if I hit the wait for the program to respond, it never does. Don't know if it's my PDF printing program causing this issue or as it happens with both my 2015.4 version and my 2016.2. Maybe I'll try a sample company and print once to my printer to see if it does it again.

Does the business number of this business start with a 7?

No. It does the same thing for all my clients. I did try printing straight to my printer and it worked ok. Seems to only happen when I print to PDF.

It's probably more related to your choice of pdf printer drivers, than the program itself.