Supporter Extend Site/Errors

hi all,

when i try to extend a site in admin>sites i get this error:

Fatal error: Cannot redeclare akismet_init() (previously declared in /home/xxxx/public_html/xxxx.com/wp-content/plugins/akismet/akismet.php:55) in /home/xxxx/public_html/xxxx.com/wp-content/plugins/akismet/akismet.php on line 63

it does extend the site but the page has this error on it after.

help?

thanks,
gina