[Plugin: Advanced Excerpt] Replace substr() with mb_substr()

I noticed the plugin uses regular, non-multibyte string functions, like substr(). This sometimes causes problems with UTF-8 text, when the substr() cuts the excerpt in the middle of a multibyte character. Fix is simple: replace substr() with mb_substr(). This is best done conditionally, as not all PHP installations have multibyte string functions installed.

http://wordpress.org/extend/plugins/advanced-excerpt/