Since downloading a plugin, i cant log into wordpress?

Hey, i downloaded the plugin ‘Woocommerce’ for my shop template. And everything seemed fine until i tried deleting a page a message would pop up saying..

Warning: call_user_func_array() [function.call-user-func-array]: First argument is expected to be a valid callback, ‘woocommerce_price_filter_init’ was given in /home/(my username)/public_html/wp-includes/plugin.php on line 406

Error in moving to Trash.

I had then logged out. And when i typed (myurl)/wp-admin
Instead of the login page popping up, this message popped up..

Warning: call_user_func_array() [function.call-user-func-array]: First argument is expected to be a valid callback, ‘woocommerce_price_filter_init’ was given in /home/(my cpanel unsername)/public_html/wp-includes/plugin.php on line 406

Warning: Cannot modify header information – headers already sent by (output started at /home/(my cpanel username)/public_html/wp-includes/plugin.php:406) in /home/(my cpanel username)/public_html/wp-includes/pluggable.php on line 876

Really need some help! Why is this happening??? Thanks