Fatal Error with Breadcrumb NavXT

I’ve added the plugin “Breadcrumb NavXT” (because the theme I’m using requires it) and when I try to activate I get this message;

Plugin could not be activated because it triggered a fatal error.

Fatal error: Cannot redeclare class bcn_breadcrumb in /hermes/bosweb/web043/b431/ipw.theoccasionalcake/public_html/amystevensadams/blog/wp-content/plugins/breadcrumb-navxt/breadcrumb_navxt_class.php on line 28

Any ideas on how to fix this? 😛

Thanks in advance for your help!
amy