2nic on "[Plugin: WooCommerce - excelling eCommerce] wp-admin dead after upgrade to 2.0.12"

Hi, just upgraded to 2.0.12 and immediately after I activate the plugin I get an Internal Server Error (500). Then I can't use the admin anymore at all.
weird thing is that the site works correctly and the shop is functioning.
only the admin is unusable

please advise

thanks

http://wordpress.org/extend/plugins/woocommerce/