Magento Error: Cannot send headers; headers already sent in public_html/lib/Mandrill/Mandrill/Exports.php
<p>Whenever someone either requests a password change or completes checkout I am getting this exception page come up with an error code.</p>

<p>"There has been an error processing your request - Exception printing is disabled by default for security reasons."</p>

<p>I've been to the error file and it says:</p>

<pre><code>a:5:{i:0;s:114:"
Cannot send headers; headers already sent in /home/siteusername/public_html/lib/Mandrill/Mandrill/Exports.php, line 1
";i:1;s:1796:"
/home/siteusername/public_html/lib/Zend/Controller/Response/Abstract.php(148): Zend_Controller_Response_Abstract-&gt;canSendHeaders(true)
/home/siteusername/public_html/app/code/core/Mage/Core/Controller/Response/Http.php(107): Zend_Controller_Response_Abstract-&gt;setRedirect('mysite.com', 302)
/home/siteusername/public_html/app/code/core/Mage/Core/Controller/Varien/Action.php(711): Mage_Core_Controller_Response_Http-&gt;setRedirect('mysite.com')
/home/siteusername/public_html/app/code/core/Mage/Core/Controller/Varien/Action.php(689): Mage_Core_Controller_Varien_Action-&gt;setRedirectWithCookieCheck('*/*/', Array)
/home/siteusername/public_html/app/code/core/Mage/Customer/controllers/AccountController.php(752): Mage_Core_Controller_Varien_Action-&gt;_redirect('*/*/')
/home/siteusername/public_html/app/code/core/Mage/Core/Controller/Varien/Action.php(418): Mage_Customer_AccountController-&gt;forgotPasswordPostAction()
/home/siteusername/public_html/app/code/core/Mage/Core/Controller/Varien/Router/Standard.php(254): Mage_Core_Controller_Varien_Action-&gt;dispatch('forgotpasswordp...')
/home/siteusername/public_html/app/code/community/BalkeTechnologies/StoreMaintenance/Controller/Router/Standard.php(91): Mage_Core_Controller_Varien_Router_Standard-&gt;match(Object(Mage_Core_Controller_Request_Http))
/home/siteusername/public_html/app/code/core/Mage/Core/Controller/Varien/Front.php(172): BalkeTechnologies_StoreMaintenance_Controller_Router_Standard-&gt;match(Object(Mage_Core_Controller_Request_Http))
/home/siteusername/public_html/app/code/core/Mage/Core/Model/App.php(365): Mage_Core_Controller_Varien_Front-&gt;dispatch()
/home/siteusername/public_html/app/Mage.php(684): Mage_Core_Model_App-&gt;run(Array)
/home/siteusername/public_html/index.php(85): Mage::run('', 'store')
{main}
";s:3:"url";s:37:"/customer/account/forgotpasswordpost/";s:11:"script_name";s:10:"/index.php";s:4:"skin";s:7:"default";}
</code></pre>

<p>Been stuck on this ages and can't find a solution.</p>