Datatable updated by multiple threads yields datagrid problem

I have a datatable that I use to display running processes. These running
processes are spawned as different threads. I use the readerwriterlock
class to ensure that when I write to the datatable, I obtain a write lock.
The datagrid is set to have a datasource of the datatable.

The problem is that I get this error intermittently and it draws a big red X
across my datagrid:

************** Exception Text **************
System.NullReferenceException: Object reference not set to an instance of an
object.
at System.Data.DataColumnPropertyDescriptor.GetValue( Object component)
at
System.Windows.Forms.DataGridColumnStyle.GetColumn ValueAtRow(CurrencyManager
source, Int32 rowNum)
at System.Windows.Forms.DataGridTextBoxColumn.Paint(G raphics g, Rectangle
bounds, CurrencyManager source, Int32 rowNum, Brush backBrush, Brush
foreBrush, Boolean alignToRight)
at
System.Windows.Forms.DataGridRelationshipRow.Paint CellContents(Graphics g,
Rectangle cellBounds, DataGridColumnStyle column, Brush backBr, Brush
foreBrush, Boolean alignToRight)
at System.Windows.Forms.DataGridRow.PaintData(Graphic s g, Rectangle
bounds, Int32 firstVisibleColumn, Int32 columnCount, Boolean alignToRight)
at System.Windows.Forms.DataGridRelationshipRow.Paint (Graphics g,
Rectangle bounds, Rectangle trueRowBounds, Int32 firstVisibleColumn, Int32
numVisibleColumns, Boolean alignToRight)
at System.Windows.Forms.DataGrid.PaintRows(Graphics g, Rectangle&
boundingRect)
at System.Windows.Forms.DataGrid.PaintGrid(Graphics g, Rectangle
gridBounds)
at System.Windows.Forms.DataGrid.OnPaint(PaintEventAr gs pe)
at System.Windows.Forms.Control.PaintWithErrorHandlin g(PaintEventArgs e,
Int16 layer, Boolean disposeEventArgs)
at System.Windows.Forms.Control.WmPaint(Message& m)
at System.Windows.Forms.Control.WndProc(Message& m)
at System.Windows.Forms.ControlNativeWindow.OnMessage (Message& m)
at System.Windows.Forms.ControlNativeWindow.WndProc(M essage& m)
at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg,
IntPtr wparam, IntPtr lparam)

Appears to be a problem with the datagrid. These threads run at the same
time updating this datatable after acquiring a lock, but what I'm not sure
is what effect this has on the datagrid since it auto-refreshes when the
datatable changes. I'm new to threading so any ideas or suggestions here
is greatly appreciated.

Thanks,
Ben