The preceding spaces or invalid characters are probably in the descriptions of one or more of the securities that you sold. Go back and delete them, then see if you can e-file. Delete any spaces at the beginning of a description. Any character that's not a letter or number can be deleted.
It has nothing to do with whether the transactions are gains or losses, or whether they are short-term or long-term.
If you have further questions, please turn off Caps Lock.
