Hi, this morning, I try to use Masonry on Blog Type from Theme Options, usually I used Sidebar. And then, because doesn’t look good, I try to select Yes on Excerpt menu.

I decide to use my old settings, so I choose Sidebar again on Blog Type, and No for Excerpt.

Reload the homepage, and I try to click on my post, but only show white page with this error message:

“Fatal error: Call to undefined function mb_strlen() in /home/*directory*/public_html/wp-content/themes/bloggy-v2-7-4/functions.php on line 770”

It happen on all page and all post. I try to deactivate all my plugins, but still error. And I try to upload the older version of theme, 2.7.3 and the problem still there. But, when I try default WordPress theme, all my page and post is working again.

Thank you