James:

I've traced the problem to the recordsource, a table. If I remove the reference to the recordsource in the first 'dead' grid, the second 'live' grid dies. It doesn't seem to matter if the table is in the DE or opened manually, same problem. The datasession is default and there's nothing special about the table. 7 fields and one index.
The form is a modal 3 page pageframe, a child of another form. I've even placed the dead grid in the parent and it works OK, but again, if I remove the dead grid the live one dies.
Any ideas?

Thanks,
Luke