Cannot add attachment in email

Hi I wonder if anyone can help. I am trying to add a file onto an email but each time I try to do so I get the message "Message attachment cannot be added. Check to make sure the correct storage card is in the device. If your device stores attachments on a storage card, you must insert a storage card to add any files to messages." I have tried to add the file from the main memory and from the Built-in storage memory but get this message each time. I have even done a hard reset and still no luck! I have an x50v with WM2003SE. I have checked in the settings to see if the option to store attachments on a storage card is ticked but it is not - Is there anything else I may have missed in the settings? Thanks in advance.