reset boot menu

[arne anka]

i installed debian to sd card and let the script modify the boot menu so  
that debian boots per default.
but for the moment i'd like the flash to be booted on power on -- so i  
changed the script to make flash the default one.

result: kernel panic, unable to mount root.

well, i assumed teh menu to be part of u-boot and flashed u-bot.
result: see above.

aux+pwr and selecting "Boot" tells something about legacy kernel, checks  
something and finally boots.
but that's not really what i meant.

so, how do i reset the u-boot menu to factory settings?