Datagrid not showing all lines

[James Hale]

I am still having datagrid problems.
I am unable to get the datagrid to display all the records I populate it with.

I am using a form datagrid that has a single field of variable height.

If I populate it with more records (from an array) than the datagrid can show the vertical scroll appears and I can scroll the records in and out of view up to a point.

For example the datagrid I am looking at as I write this should have 20 rows.
I can only get 13 to show and even then, the 13th is only half there.

I know they are all there as the dgnumberoflines property returns the correct value.
I also have buttons that step through the datagrid and these work fine.
They move forward or back and highlight the "chosen" line as well as display it in context within another field.
When I hit the last line visible (13 in this case) pressing the forward button moves forward and displays the next line in context but the datagrid itself does nothing.
I can move through to the end and back again.
Once I hit the record showing at the bottom of the datagrid everything starts behaving as it should.

I have deleted the datagrid and redone it. But no change.
The only modification I carried out on the form was to change the single field's name and set its text style.

Any thoughts?

James