ERR (3): Notice: iconv_

[antrax13]

H,

I have this error in system.log:

ERR (3): Notice: iconv_substr(): Detected an illegal character in input string in /var/www/vhosts/XXXXXXXX.com/httpdocs/app/code/core/Mage/Core/Helper/String.php on line 103

How can solve this?