Q: I entered the BitLocker recovery key on my computer as the boot information changed, powered off, and turned on my machine again, and it’s still prompting for the recovery key. What do I do?

A: If anything changes around the boot configuration of your machine, BitLocker prompts for the recovery key before you can continue using the machine. (By the way, many actions can cause changes to the boot configuration, including BIOS updates; find a full list of causes at the Microsoft article "BitLocker Drive Encryption in Windows 7: Frequently Asked Questions.") 

To fix this, after you boot into Windows, you must suspend, then resume, BitLocker. This resets the boot information and avoids the need to enter the recovery key again. To suspend, then resume BitLocker, do the following:

You should no longer be prompted for the recovery note. Ideally, you should actually perform the BitLocker suspend action before making changes to BIOS and disks, then resume Bitlocker after you've made all your changes. That way, you won't have to enter the recovery key at all.