Found my upgrade problem - as I suspected - a new Toolbar appeared after Zone Alarm firewall upgraded. It was called Zone Alarm Spy Blocker Toolbar but was a repackaged AskToolbar, and showed up as Ask Services I think in Process Explorer.
I finally found it in Firefox add-ons and removed it - slow -crashing - switching tabs by itself randomly - all problems went away. Zone Alarm added it but I didn't see an indication on where it was coming from.
It also caused pages to load slowly - 30 seconds to a minute or more - I'm used to a split second or two and was rather frustrated the whole day.