Magento

Hi Everyone,
When I checkout on the site using paypal express, it returns to my Magento store to check the order details and place the order, but when I do so, I get the following error (Although the payment goes through).  I can’t seem to fix it.  Any help with this would be greatly appreciated!: 

a:5:{i:0;s:99:"Cannot send headers; headers already sent in /home/grshop/public_html/lib/Zend/Currency.php, line 1";i:1;s:1357:"#0 /home/grshop/public_html/lib/Zend/Controller/Response/Abstract.php(148): Zend_Controller_Response_Abstract->canSendHeaders(true)
#1 /home/grshop/public_html/app/code/core/Mage/Core/Controller/Response/Http.php(105): Zend_Controller_Response_Abstract->setRedirect(’https://grshop....’, 302)
#2 /home/grshop/public_html/app/code/core/Mage/Core/Controller/Varien/Action.php(672): Mage_Core_Controller_Response_Http->setRedirect(’https://grshop....’)
#3 /home/grshop/public_html/app/code/core/Mage/Paypal/Controller/Express/Abstract.php(315): Mage_Core_Controller_Varien_Action->_redirect(’*/*/review’)
#4 /home/grshop/public_html/app/code/core/Mage/Core/Controller/Varien/Action.php(420): Mage_Paypal_Controller_Express_Abstract->placeOrderAction()
#5 /home/grshop/public_html/app/code/core/Mage/Core/Controller/Varien/Router/Standard.php(250): Mage_Core_Controller_Varien_Action->dispatch(’placeOrder’)
#6 /home/grshop/public_html/app/code/core/Mage/Core/Controller/Varien/Front.php(176): Mage_Core_Controller_Varien_Router_Standard->match(Object(Mage_Core_Controller_Request_Http))
#7 /home/grshop/public_html/app/code/core/Mage/Core/Model/App.php(349): Mage_Core_Controller_Varien_Front->dispatch()
#8 /home/grshop/public_html/app/Mage.php(640): Mage_Core_Model_App->run(Array)
#9 /home/grshop/public_html/index.php(80): Mage::run(’’, ‘store’)
#10 {main}”;s:3:"url”;s:27:"/paypal/express/placeOrder/”;s:11:"script_name”;s:10:"/index.php”;s:4:"skin”;s:5:"ca_en";}

Thanks,
Crispin

Hi - Sorry to bump this, but I would really appreciate some help - my customers keep complaining to me.
Thanks!