Strange Warning

I’m using Pinboard 1.09. I’ve been getting this warning message across the top of my page.

Warning: join() [function.join]: Invalid arguments passed in /hermes/bosoraweb129/b1596/nf.borderlandteachers/public_html/wp-includes/post-template.php on line 389
class=””>

Don’t know what caused it. I’ve been keeping-up with updates but that’s about all. The message goes away if I change themes.

http://www.borderlandteachers.ca

K