[Plugin: HeadSpace2 SEO] HeadSpace Debug warning

when i enable debug i got this====>

Warning: Cannot modify header information - headers already sent by (output started at /home/vhs54236/public_html/wp-content/plugins/headspace2/models/headspace.php:344) in /home/vhs54236/public_html/wp-content/plugins/mingle-forum/wpf.class.php on line 1608

and i have no idea what this is?

when i go to my site with this enable everything is out of place.
so i disabled it.

I would like to know what to do about this warning… when i go to my site in IE my browser closes and open backs up and im not sure if its because of this or its from another plugin

please help?

thankz ??