Проблема решена, помог Petrov.Sergey. Спасибо!
Вот решение в примере:
@Test
public void testSample() throws Exception {
driver.get(baseUrl);
driver.findElement(By.id("loginContainer_username")).clear();
driver.findElement(By.id("loginContainer_username")).sendKeys("da");
driver.findElement(By.id("loginContainer_password")).clear();
driver.findElement(By.id("loginContainer_password")).sendKeys("da");
driver.findElement(By.name("loginContainer$ctl05")).click();
driver.findElement(By.id("tdImbButtonmenu_2")).click();
driver.findElement(By.id("manageFilter_ctl00_filterItem_buttonEnter_popupButton")).click();
Set<String> windows = driver.getWindowHandles();
Iterator<String> it = windows.iterator();
String mainWindow = (String) it.next();
String popUp = (String) it.next();
driver.switchTo().window(popUp);
driver.findElement(By.id("itemDataGrid_ctl03_ctl05")).click();
driver.close();
driver.switchTo().window(mainWindow);
}