Checkout out Error

Urgent need to fix the following errors. Need to fix within next 2 hours. 1)In the "Contact Us" page when form is filled up and clicked on Submit this shows the following error: Warning: Cannot modify header information - headers already sent by (output started at C:\Sites\Single46\thehcgdrops\webroot\includes\classes\[login to view URL]) in C:\Sites\Single46\thehcgdrops\webroot\includes\functions\[login to view URL] on line 33 2)When you are checkout and use your credit card it says that you have not filled out all the required informaion. Though the order is placed but we are not getting any payment. Its very urgent. Bid only if you can fix this within next 2 hours.