I was having some problems with my laptop's Bluetooth radio turning itself off when I reboot without powering off. I found an online posting indicating resetting the BIOS to defaults would fix the problem. I went into the BIOS setup and reset it then rebooted. However, that changed the system enough to make Bitlocker to ask for the recovery key. I put in the recovery key then suspended Bitlocker on the C drive after Windows came up (as the Bitlocker message instructed). I then resumed Bitlocker and it seemed to work after another reboot. [more]
However, when I rebooted the laptop at home later that day, Bitlocker asked for the recovery key again. I found another Microsoft support entry that indicated the problem might be that the boot order was changed. That made sense because my configuration at home involved an external USB device that wasn't connected at the office.
I suspended Bitlocker then rebooted and went into the BIOS setup and made sure the first (and only in this case) boot device listed was my C drive.
After rebooting, I resumed Bitlocker protection and haven't had a problem since.