You should follow this uninstall guide Doug has created but bottom line you want to wipe your mac clean of 4.8.3 and stuff is in about 5 different places or more so look around.
http://www.captureintegration.com/2008/11/...e-one-4-on-mac/I even go this far and really wipe the system and since you are doing a upgrade here in a completely new version. I would recommend doing this bottom section
[User] > Library > Application Support > Capture One
[User] > Library > Preferences > com.phaseone.[anything]
[User] > Pictures > Capture One Default Session
[User] > Pictures > Capture One Library
[HD] > System > Library > Application Support > Capture One