I encountered an issue on a HP 6540b Laptop with Windows 7 after the OS volume is encrypted with Bitlocker, the system never starts up normally. Every time the system is shutdown completely and then started again, it brings up the Bitlocker console and wants the recovery key entered. It doesn’t seem to do this when the system is restarted with CTRL+ALT+DELETE
After updating to the latest HP BIOS the problem was fixt.
Download the Latest bios update from the HP site for the 6540b HERE.