an eror ??? >

hi
i install this plugin on my Multisite,
(( cimy user extra fields ))

but, i see an error on register form 🙁

Warning: session_start() [function.session-start]: Cannot send session cache limiter – headers already sent (output started at /home/fizilyco/public_html/wp-content/themes/suffusion/header.php:26) in /home/fizilyco/public_html/wp-content/mu-plugins/cimy-user-extra-fields/securimage/securimage.php on line 513

i install plugin by this link:
http://wordpress.org/extend/plugins/cimy-user-extra-fields/installation/

how can i do?
please help me ,
thanks