Same problem here on a XAMPP localhost install. Upgraded from 3.4.1 to 3.4.2 just now and site is trashed. There was an error during the plugin install that said it could not completely delete the plugin folder and then all heck broke loose! The woocommerce plugin was partially empty, I deleted it and copied over a backup, even that was no good.
I do have 3rdParty and my own custom plugin, one of those may be the problem but, 3.4.1 was working fine. Also, why would a 3rdParty plugin cause the woocommerce update to fail?
