I have now managed to check all my seeds against version 0.3 and most of the words are rejected. So now back to square one.
Maybe it was a different version of Electrum, maybe it was some other random wallet type whose name I can't remember. What a nightmare.
The alpha release used "passphrase" instead of a seed/mnemonic.Maybe it was a different version of Electrum, maybe it was some other random wallet type whose name I can't remember. What a nightmare.
Perhaps your invalid menmonics are actually passphrases used to generate old Electrum wallets.
See if you can run it: https://github.com/spesmilo/electrum/tree/368fa7980f74db07e22eb32edf292abeb98b8d82