It wouldn't have anything to do with the video card driver since it is only first loaded well into the booting session, much later then when the bios screen is active.
Since it has happened at the same time as the Vista loadup instead, you might find success by fixing that.
Open an elevated command prompt. Then copy paste this command and press enter:
Code:
bcdedit /set {current} locale en-US
Reboot. If still the same, then try this command:
Code:
bcdboot %WinDir% /l en-US
EDIT - Just noticed that you said the boot was fixed. You can use this post if you ever run into the problem again. It happens when you edit the bcd and the locale entry is not set right...or when you do a startup repair with Vista DVD.