Error with Unpluggable – Help

Hi,

I have several wordpress installations on the same server and they all seem to be having a similar issue. Depending on whether the www. is there or not they throw up this error

Warning: Cannot modify header information – headers already sent by (output started at /home2/youthwo1/public_html/hcyt/index.php(1) : eval()’d code:37) in /home2/youthwo1/public_html/hcyt/wp-includes/pluggable.php on line 897

For example with youthworkresource.com if I don’t have www. I get the error but if I add www. I don’t. I have the exact opposite with hcyt.co.uk and I have no idea to fix it

Has anyone had this problem? Know how I can fix it?

Thanks