What OS, and are you installing Opera for multiple user accounts?
Are you using any add-ons/extensions with Opera? If so, try either shutting them down or removing them.
Also, when you reinstall, have you tried installing into a different-named folder than the earlier installations were put into (eg, not "*\opera" but instead something like *\opera1216)? When Opera is installed into a folder, it immediately looks for left-behind files from earlier installations in that folder and auto-imports them, if any are present (along with any file corruption they may contain). Even if you "delete the install folder" but have separate user accounts, their similar-named user folders (located under AppData or ApplicationData) will remain to possibly corrupt a new install if made into that same previous folder name.