I did the purge and all went well until the uninstaller came up. After a minute or two it said on top (not responding). So I closed it with task manager, used iobit to finish the uninstall (it had left 7.49 mb behind) the rebooted. I got a black screen, cursor only, during the uninstall and it took a while to come up to the full desktop. After that installed 10.72 beta without any problems. No black screen nor delay in applying another skin. Works. (fingers crossed).
BTW: It still doesn't skin Chrome.