This is a recent Bento bug.
For More Information see: Unable to import Bento database
This is one of many acknowledged bugs that can be found in the Known Bug List here in the Report an Issue section of the forum.
It can also be downloaded as a database file from: http://www.4shared.com/file/8orL8apk/FMP_Bugs.html
Thanks for responding to quickly.
I've looked at the other thread (sorry, I had searched before posting my own thread, but not seen the earlier one).
I guess I'll have to export Bento data in csv or xlx format for a while, until they fix the bug.
Thanks again for your invaluable help.