If you back up your wallet frequently, you can just restore the backup since the spent coins won't be confirmed.
yes they will.It worked for me. Maybe it was a bug.
was it in the difficulty-way-too-high-time before merged mining?
It wasn't a namecoin that was spent, but a bitcoin that went to an invalid address that did not get confirmed. I thought this would be the same type of error. It was during the time when DD attacks were going on.
the client will discard a address if the prefix invalid, but the whole address is not in the transaction, only the hash.
in the good old times, when namecoin did not have their own prefix, there was no diffrence between bitcoin and namecoin addresses.
the hash + checksum, is just a hash of a public key, which can be used on both networks.
