Then you're not doing something too similar, because that's quite
different to the error in the post you quote. It involved file fields,
but that's it.
So what are you doing to trigger this error? What's a really small
example that demonstrates the problem?
Based on the error, you may have found the same thing as ticket #10249,
in which case the solution is to wait for that to be fixed. It's on the
1.1 milestone.
Regards,
Malcolm