[Plugin: WP-dTree] v3.5 Menu disappearing off homepage

Hi,

if I tick the ‘Open to selection’ option the wp-dtree menu no longer shows on the homepage.

Homepage is https://www.wyndhamhousedental.co.uk/cms/
All other pages display the menu:
eg. https://www.wyndhamhousedental.co.uk/cms/about-us/

The source on the homepage shows an error being generated:
<b>Warning</b>: substr_count() [function.substr-count]: Empty substring in <b>/home/wyndhamh/public_html/cms/wp-content/plugins/wp-dtree-30/wp-dtree_gen-functions.php</b> on line <b>180</b>

All advice appreciated,

Many thanks,

Byron