Made no major changes...
Have you changed the tooltypes of OWB, or moved the binary? Did the problem start precisely after you changed your screen resoulution? Is OWB on its own screen? Does it start with a blank page or a given URL? Have you tried the URL (or any other page) in IBrowse?
How much RAM is installed in Samantha .. 1GB machines had some trouble with the last OS-Update. Do you use a big wallpaper? Have you changed your USB-Setup (e.g. are you using a new hub)? Are you starting OWB from AmiDock? What dockies are in your Dock?
I´d look into these sort of things. I am using OWB 3.15 on a daily basis and it is quite stable. I don´t think it is rensible to reinstall the OS. You could remove some stuff you installed in WBStartup or User-startup maybe?
