Bug? on Password protected pages..

Guys I think I have a bug.

With this plugin activated I cannot password protect pages on my site. Instead, when someone (regardless of status) enters the password on a protected page they are instantly redirected to their main admin page. The protected page is inaccessible.

Deactivating the plugin makes the problem go away.

Any idea?

http://ww.wp.xz.cn/extend/plugins/custom-registration-link/