Sick of entering your serial every time you play? Right underneath the "Forgotten Password" button on the login screen, there's an option to save your serial number so you don't have to enter it every time. This also (for me) fixes the "serial number already in use" issue.
If this works for you, vote to sticky the thread.
EDIT: Also, if this works for you, please don't use this forum as your personal blog/vent spot. Really tired of seeing "BAAAAAWWW CRYTEK svckS THIS GAME IS BROKEN!!!!!!111`" posts. Thanks.