[Plugin: WooCommerce – excelling eCommerce] Can't update Woocommerce

Hi,

I’m trying to update my Woocommerce version from 1.5.8 to 1.6.4 but got the following message that says update failed.

Update Plugin
Downloading update from http://downloads.wordpress.org/plugin/woocommerce.1.6.4.zip…

Unpacking the update…

Installing the latest version…

Removing the old version of the plugin…

Could not remove the old plugin.

Plugin update failed.

Does anyone know how to fix this? Thank you so much!

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