Domain Mapping Error: Warning: Cannot modify header information

I just srarted getting this error when I try to login to one of my sites on my network. I am not sure if upgading this plugin caused the error? I am on most recent version of WordPress and most recent version of the Domain Mapping plugin.

I deactivated the plugin from network and I stop getting the error. I'm not sure what deactivating will do to my network of sites using their own domains.

How do I fix this error below when trying to login?

If it doesn't redirect in 5 seconds please click here.

Warning: Cannot modify header information - headers already sent by (output started at /home/drescher/public_html/wp-content/plugins/domain-mapping/domain-mapping.php:301) in /home/drescher/public_html/wp-content/plugins/domain-mapping/domain-mapping.php on line 325

Warning: Cannot modify header information - headers already sent by (output started at /home/drescher/public_html/wp-content/plugins/domain-mapping/domain-mapping.php:301) in /home/drescher/public_html/wp-content/plugins/domain-mapping/domain-mapping.php on line 326