Hi there,
First off, it's a beta and they are meant to have issues. Seems like you found an issue and if you want to make the sim better, file a bug report so the devs have access to your problem and find a solution. To go back to stable 10.45, redownload the updater /installer from the main XP website under downloads, run the installer and uncheck "check for new betas" then proceed.
-Rishi