I don't believe there was a solution, but like you said, it appears the history was not converted.

I actually brought one of the client's old machines back on line with plus (it's own copy of the Plus database, not the current) so that they could use it for reference.

On another note (perhaps I should start a new thread?) have you heard of people having their paid AR transactions deleted instead of going to history at year end? (No, they didn't select 'clear history).