i faced a problem during running the code in selenium rc please solve it

if i run this code only one time the prestashop app store item added into cart and error occured like
Exception in thread "main" java.lang.IllegalMonitorStateException
at java.lang.Object.wait(Native Method)
at java.lang.Object.wait(Object.java:485)
at nonRep.testUntitled(nonRep.java:47)
at nonRep.main(nonRep.java:70)
please solve the prob




import com.thoughtworks.selenium.DefaultSelenium;
import com.thoughtworks.selenium.SeleneseTestCase;


public class nonRep extends SeleneseTestCase {


public void setUp() throws Exception {
selenium = new DefaultSelenium("localhost", 4444, "*firefox", "https://www.google.co.in/");
selenium.start();
selenium.windowMaximize();
}


public void testUntitled() throws Exception {
selenium.open("http://localhost/prestashop/index.php");


selenium.click("css=a[title="Now that you can buy movies from the iTunes Store and sync them to your iPod, the whole world is your theater."]");
selenium.waitForPageToLoad("60000");

String text=selenium.getText("//*[@id='center_column']/div[2]");
String[] temp=text.split(" ");
int n2=Integer.parseInt(temp[2]);
System.out.println(n2);
Number n=(selenium.getXpathCount("//input[starts-with(@id,'comparator_item')]"));

System.out.println(n);


int i;
for (i=1;i<=n2;i++)
{


selenium.click("//*[@id='categories_block_left']/div/ul/li[1]/a");
selenium.waitForPageToLoad("60000");
String s="//*[@id='product_list']/li["+i+"]/div[2]/a/img";
System.out.println(s);
selenium.click(s);
selenium.waitForPageToLoad("60000");
if(selenium.isElementPresent("//*[@id='add_to_cart']/input")) //finds the button
{
selenium.focus("//*[@id='add_to_cart']/input"); // focuses the button
selenium.highlight("//*[@id='add_to_cart']/input"); //highlights the button

selenium.click("//*[@id='add_to_cart']/input"); //doesn't click the button???
selenium.wait();
}




}


}




public void tearDown() throws Exception {


}
public static void main(String[]x)throws Exception

{
nonRep r=new nonRep();
r.setUp();
r.testUntitled();
}

}