Hi,
thank for reporting.
To fix the bug please open iemview.pas and replace CalcGridWidth method (at the bottom of the source code) with this one:
function TImageEnMView.CalcGridWidth():integer;
begin
case fGridWidth of
-1: result := (clientwidth - fHorizBorder) div (fThumbWidth + fHorizBorder);
0: result := ImageCount;
else
result := fGridWidth;
end;
end;
A fixed version will be released ASAP (which will fixe also the bug with semi-transparent selection and GridWidth=0).