Cannot open the URLs on the page using Selenium webdriver and Java - selenium

Question

I have written a code using Selenium webdriver and Java to open the URL listed in one particular div on the webpage.
The code opens the first URL goes back to the webpage and the throws the error "Element not found in the cache" - perhaps the page has changed since it was looked up.
Please find the code for reference.
import java.util.*;
import org.openqa.selenium.By;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.WebElement;
import org.openqa.selenium.firefox.FirefoxDriver;
public class OpenLinks {
public static void OpenLinkAs(String username, String password) throws Exception
{
WebDriver driver;
driver = new FirefoxDriver();
driver.get("http://stg.n**w.le****ine.com/");
driver.findElement(By.name("username")).sendKeys(username);
driver.findElement(By.name("password")).sendKeys(password);
driver.findElement(By.xpath("/html/body/div/div/div[2]/div/form/p[3]/input")).submit();
String content = driver.getPageSource();
if (content.contains("Create new Project"))
{
List<WebElement> elementsList = driver.findElements(By.xpath("//div[#class='recent-project block-link']"));
int RowCount = elementsList.size();
System.out.println(RowCount);
System.out.println(elementsList);
for (int i = 0; i < RowCount; i++)
{
//String oldTab = driver.getWindowHandle();
WebElement url = elementsList.get(i);
//String text= url.getText();
System.out.println(url);
// System.out.println(text);
url.click();
Thread.sleep(5*1000);
driver.navigate().back();
//driver.switchTo().window(oldTab);
}
}
}
public static void main(String[] args) throws Exception
{
OpenLinkAs("username", "password");
}
}

Answer 1

If the element is not found on the page its likely to have been dropped in the DOM. Declare t again and attempt to click it.
What is being returned in the stacktrace, i.e. at what point in the code is the error thrown at?