Did you use the Arduino IDE to install the bootloader?If yes, which board did you have selected?
Now that I think about it, I think I used avrdude to install it.
Did you set the "lock bits"?
If I use USBtinyISP to burn the bootloader from the IDE, does it select the .hex file to use based on the IDE:Board setting
or is there an additional dialog where you set that?
From your comments, I presume it takes care of all the fiddly-bits as well?