I'm having issues with WooCommerce 2.1.1 as well. I changed some text on a tab in this plugin and even though I've changed it back, I keep getting a warning message:
Warning: Cannot modify header information - header already sent by (output started at ... in my functions.php). I cleared my functions.php file, but still get the error message.
My website still seems to be functioning, though displays the warning.
Any help on this would be highly appreciated. :)