In most cases for softmodding video cards, flashing the bios will make your current card think its a totally different card. This was a real good thing a while back, when some of the cards ATI were making had pipes in them that were hardlocked. In those cards cases, flashing the bios to a different higher end card (when it was possible) got you the extra pipes unlocked. In some other cases, like the poster above re-flashing the bios for him will pretty much reset his card to a more stable/bootable speed(s).
Also, in my own experience I have a powercolor 9550, that is flashed to a 9600 pro w/ modded memory speeds. This allows me to use ATI's drivers instead of third party ones, homebrewed ones,.. etc. Hope that was informative. Btw, hi to everyone here too, I'm still new here, and I'm glad sites like this are around so I can learn too.