[Plugin: NextGEN Gallery] Problem with nextgen compatibility

hi!
i made a plugin that generates a file and send it directly to the user (in the admin backend). so i have to send custom file headers which i send over the “init” action hook. it works great without the nextgen gallery plugin, but until i activate the nextgen plugin it seems to send headers too (Warning: Cannot modify header information – headers already sent by (output started at …plugins\nextgen-gallery\admin\manage-images.php:952)). is there any way to suppress it (supress the action of nextgen here), or is there an other hook for the admin area like “template_redirect”??!!! maybe you could help me with that problem.

ps: sorry for my bad english ??