Crystal Report Shows Weird Symbols

I am facing this problem when i send Dataset to crystal report it shows me weird symbols as seen in the the image below sometimes if i refresh it works and with Mozilla Firefox though it sometimes works is there any Suggestion to solve this ??? please check the image of the problem 

Image may be NSFW.
Clik here to view.

Notice I use Memorystream to display the crystal report onside the webpage  as Below and I use VS2010 with SAP Crystal Report

report.SetDataSource(DS);

        MemoryStream oStream;
        oStream = (MemoryStream)report.ExportToStream(CrystalDecisions.Shared.ExportFormatType.PortableDocFormat);
        Response.Clear();
        Response.Buffer = true;
        Response.ContentType = "application/pdf";
        Response.BinaryWrite(oStream.ToArray());
        Response.Flush();
        Response.Close();