Images are shrunken => i want to get them shrink-proof

[tronix01]

Hello @ all I have a problem with my generated PNG - Images. It's a bit strange for me but may be someone now what i can do to solve this problem. My windows service create on the fly PNG - Images and store them as binary in a database. The stored images are displayed later with a crystal report in a windows app. That works very fine since years and also with different pc's (most XP-OS), but there is a problem with a new PC (XP-OS) since a few days. All images are displayed shrunken in the reports and it's not the whole report.... only the images. Text- and Report still proportional. Could it be that something is missing at the new machine ? Any ideas how this could be ? Thanks a lot!

Bitmap couponImg = null;
Font font = null;
Graphics graphic = null;

try
{
couponImg = new Bitmap(coupon.Width, coupon.Height, PixelFormat.Format24bppRgb);

 using (graphic = Graphics.FromImage(couponImg)) //V1.01.03.01
      {
        graphic.Clear(coupon.BackgroundColor);
 
        graphic.InterpolationMode  = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
        graphic.PixelOffsetMode    = System.Drawing.Drawing2D.PixelOffsetMode.HighQuality;
        graphic.TextRenderingHint  = System.Drawing.Text.TextRenderingHint.AntiAlias;
        graphic.TextContrast       = 0;
        graphic.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;
        graphic.SmoothingMode      = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;

        if (coupon.couponCellCollection != null && coupon.couponCellCollection.Count > 0)
        {
          for (int idx = 0; idx < coupon.couponCellCollection.Count; idx++)
          {
            font = new Font(coupon.font, (float)coupon.couponCellCollection\[idx\].fFontSize, FontStyle.Bold, GraphicsUnit.Millimeter);

            graphic.DrawString(coupon.couponCellCollection\[idx\].sCellValue, font, Brushes.Black, new PointF(coupon.couponCellCollection\[idx\].iPosX, coupon.couponCellCollection\[idx\].iPosY));

            font = null;
          }
        }
        graphic.DrawImage(couponImg, new Rectangle(0, 0, coupon.Width, coupon.height), 0, 0, coupon.Width, coupon.height, GraphicsUnit.Pixel);
    
        graphic.Flush(); //V1.01.03.01
      }
}
 }
 catch (Exception)
 {
couponImg = null;
 }
 finally
 {
    if (graphic != null)
    {