Headers already sent/Invalid argument supplied foreach

Logging on as a subscriber in IE throws a ‘headers already sent’ error referencing lines 563/564 in wp-includes/option.php and Warning: Invalid argument supplied for foreach() in /######/wp-content/plugins/fundraising/fundraiser.php on line 921

####Error Message Start####

Warning: Invalid argument supplied for foreach() in /–/–/public_html/wp-content/plugins/fundraising/fundraiser.php on line 921

Warning: Cannot modify header information – headers already sent by (output started at /–/–/public_html/wp-content/plugins/fundraising/fundraiser.php:921) in /home2/lymeprot/public_html/wp-includes/option.php on line 563

Warning: Cannot modify header information – headers already sent by (output started at /–/–/public_html/wp-content/plugins/fundraising/fundraiser.php:921) in /–/–/public_html/wp-includes/option.php on line 564

####Error Message End ###

Theme = Catalyst Dynamik

WP = 3.4.2 Multisite

Deactivating the Fundraising plugin solves the issue but I need to use it as this is a charity site.

Please advise.