[cross post from /r/electrum in fairly depserate hope of an answer]
So, I think I just seriously fucked up. I created a new electrum wallet with a Bip39 seed phrase and tried to extend it with a custom word. I have done this many times before. But, this time I really fucked up. Rather than entering the custom word on the next screen AFTER entering the seed, I entered the custom word WITH the seed, so that my seed ended up being 25 words long and using a word not in any wordlist. The wallet generated and I sent a large amount of BTC to one of the addresses. Now I can't move it; I get an error that the transaciton was rejected by the network b/c the mandatory script verify flag failed, false/empty top stack element (code 16).
If I look at the correctly formed bip39 seed without the 25th word, it has a different public address than my malformed seed generates, but both addresses uses the same private key.
Anyone have any ideas? If this money is gone, I am really, really fucked.