Yes, you're basically screwed if this happens

IMO reading trough a lot of posts regarding this topic the only permanent method to solve this is described here by Dongle Fongle https://talk.maemo.org/showpost.php?...&postcount=207

I tried it too, but failed - you need to be careful not to fry the motherboard in an oven but still make it hot enough for a certain period of time to have a successful reballing effect.

With patience and start slowly - not every oven is the same I think this method should work.
I lack the patience (I still have a few spare N900's) and probably baked mine too long and made it too hot. Dongle Frongle might give you some pointers as well - I think he is still around.

You are pretty unlucky with your N900's unfortunately that is the risk with these old phones and the reason why so many of us have spares. I have lost two N900's because of this error.