PAF 4 will cause you no problems in running side by side with PAF 5. Matter of fact, I have versions 2.31, 3, 4, and 5 all still on my computer, as well as German versions of 4 and 5. So there is no need to uninstall 4.
If you have reinstalled PAF 5 again, in the manner I described previously, you may have a problem in your computer somewhere. Just a couple of thoughts: what other programs are you running at the same time? What amount of RAM do you have available. I ask these questions because, without seeing what happens, it sounds like your computer is getting "bogged down" and is refusing to move. A sympton of too many activities drawing on your computer's resources. That may be an angle to investigate, but I am not saying it is the solution - just can't think of what else it would be.
This product may be similar to Conflict Catcher: http://download.cnet.com/downloads/0-10102-100-5739564.html?tag=st.dl.10001-103-1.lst-7-1.5739564http://download.cnet.com/downloads/0-10102-100-5739564.html?tag=st.dl.10001-103-1.lst-7-1.5739564 It's called BigFix and is a utility that fixes bugs and viruses before they create problems. BigFix is designed for early detection of configuration conflicts, bugs, or viruses in your computer. It then provides quick, automated solutions for dealing with problems before they bother you. Recent updates have included an improved diagnostic engine, a new help system and tutorial, and faster synchronization with sites. I have not used this product.