Problem displaying rows after deletion in scrollable grid

I'm trying to delete a number of rows in a grid with a vertical scrollbar. I After selecting a number of rows, I call the deleteRow function provided by the grid control with each of the indices.

After scrolling down in the grid, the following effects can be noticed. (Example grid setup is 20 rows in the grid with 10 rows visible at any 1 time):
- When one or two rows are deleted from near the bottom of the grid, the grid is displayed with white space beneath the last row. Once the vertical scrollbar is used, this white space disappears.
- If all the rows that are currently visible are deleted, only the rows that were beneath the selection are displayed, e.g. If I selected rows with indices 7-16, the rows 18 and 19 would be displayed. However after moving the horizontal scrollbar, the rows 0-6 are also displayed.

Is there a setting to refresh the scrollbar settings??

Thanks, Helen.