i've had to do a couple of things to fix this, the end of my code now looks like this:
finally
{
if (wrdApp != null)
{
Object oSaveChanges;
oSaveChanges = false;
((_Application)wrdApp).Quit(ref oSaveChanges, ref oMissing, ref oMissing);
wrdApp = null;
}
OpenFileForUser(strFolderPath, strFileName);
}
}
protected void OpenFileForUser(string strFolderPath, string strFileName)
{
Response.Clear();
Response.ContentType = "application/ms-word";
Response.AddHeader("Content-disposition", "inline; filename=" + strFileName);
String path = strFolderPath + @"\" + strFileName;
Response.WriteFile(path);
Response.End();
}
the btnGenerateCallSheet was inside an UpdatePanel so I've added the following trigger to my front end page
<triggers>
<asp:postbacktrigger controlid="btnGenerateCallSheet" xmlns:asp="#unknown" />
</triggers>