Profiles and reinstalling? Would be way too complicated for me, I just simply copy sometimes the whole KM-folder (where also my profile is in), and voila have a backup of everything. No prob, couldn't be simpler!
Neither did I install it in the first place, just download, unzip, create an empty file "profile.ini" in it, and it's portable right-away. Which version I then start doesn't matter, they're independant. Anything messed? Just copy over either the prefs.js from the profile, or the whole profile, or simple the whole KM folder... The bookmarks are also just one single html-file inside the folder, easy to copy for backup. Same for hotlist.
So just leave your existing installation alone, a backup copy never can harm, and unzip a fresh KM to try ;-)