I got this error when installed new modules

hi ..

I always had this error when i installed a new module.

Warning: Cannot modify header information - headers already sent by (output started at /home/dapurpix/public_html/mekar/modules/boonex/store/classes/BxStoreModule.php:1239) in /home/dapurpix/public_html/mekar/inc/admin_design.inc.php on line 56

the error path is vary depend on the modules that i installed.

Could anyone help me fix this please ??

Im using D 7.0.2

thanks

hello ...

anyone ???

I would check the files to see if there is any 'white space' after the closing php code ?>