>
> They are different. The first one is older
>
> Yes, they are/were different, but the version in TL was newer, not older.
>
Maybe. I saw "Version 1.1", so I decided it's newer.
> Evidently a regression of some sort, since the older biblatex.4ht worked
> and the newer one didn't. Can you please confirm that your failure is
> with biblatex.4ht {version 2012-09-28-15:51}, as checked into TL?
>
I confirm. I removed and installed tex4ht with tlmgr, and have the same
error as before. And as before, removing \relax from 4oo file makes the
error disappear. The version of biblatex.4ht is 2012-09-28-15:51.
