Hi,
the first question is: is your notebook placed directly on a wxFrame? If so, try to place a wxPanel on the wxFrame, then the notebook on this panel. You might have the same problem as described here: http://lists.wxwindows.org/cgi-bin/ezmlm-cgi?8:msp:53034:fonomokgdfmdkaiiipco
Have you tried to enclose the changes in your grid between wxGrid::BeginBatch() and wxGrid::EndBatch()? This should reduce flickering.
HTH,
Cristina.