Error when trying to login using selenium webdriver in IE11 - selenium-webdriver

Question

I am getting the below error when i try to login and select a drop down in login page using selenium webdriver in IE11.
[{
DesiredCapabilities capabilities=DesiredCapabilities.internetExplorer();
capabilities.setCapability(InternetExplorerDriver.INTRODUCE_FLAKINESS_BY_IGNORING_SECURITY_DOMAINS, true);
System.setProperty("webdriver.ie.driver", "C://Users//chetana.inamdar//Desktop//selenium//IEDriverServer.exe");
WebDriver driver = new InternetExplorerDriver(capabilities);
driver.navigate().to("url");
driver.findElement(By.id("ctl00_plhContent_txtUserName")).sendKeys("username");
driver.findElement(By.id("ctl00_plhContent_txtPassword")).sendKeys("Password");
driver.findElement(By.id("ctl00_plhContent_btnLogin")).click();
driver.manage().timeouts().implicitlyWait(120, TimeUnit.SECONDS);
//Select dropdown=new Select(driver.findElement(By.xpath(".//*[#name='ctl00$plhContent$Tabs$pnltabPermanentArea$ddlIDSearch']")));
Select dropdown=new Select(driver.findElement(By.name("ctl00$plhContent$Tabs$pnltabPermanentArea$ddlIDSearch")));
dropdown.selectByValue("CS Number");
System.out.println("the output of selected is"+driver.findElement(By.id("ctl00_plhContent_Tabs_pnltabPermanentArea_ddlIDSearch")).isSelected());
driver.findElement(By.id("ctl00_plhContent_Tabs_pnltabPermanentArea_txtIDSearch")).sendKeys("1234");
}]
Error: