Massive drop in performance (fixed after reboot)

People seemed to have jumped on the single reboot I mentioned. Old habits die hard, and I reboot after every largish piece of software I install. Including the first instance of this unstable build. Also the second.

 

A sensibly amended title would read "solved after 2 downloads, 3 installs ,3 reboots, 2 helpful replies and a pedantic debate about if the title was misleading". Sadly I didn't amend the title.