Program: 7900
Project: 7900
Buggy source:
public void run(){
  while (enabled) {
    try {
      Set<Entry<Player,Long>> set=timeStamp.entrySet();
synchronized (sync) {
        Iterator<Entry<Player,Long>> it=set.iterator();
        while (it.hasNext()) {
          Entry<Player,Long> next=it.next();
          if ((System.currentTimeMillis() - timedelay) > next.getValue()) {
            Player reciever=playerMap.remove(next.getKey());
            Player sender=recieverPlayerMap.remove(reciever);
            it.remove();
            if (sender != null && reciever != null && sender.isOnline() && reciever.isOnline()) {
              ItemStack item=sender.getInventory().getItemInHand();
              if (item.getTypeId() == itemId && item.getAmount() >= amountRequired) {
                item.setAmount(item.getAmount() - amountRequired);
                if (item.getAmount() <= 0) {
                  sender.getInventory().remove(item);
                }
                if (reciever.getHealth() + healamount > maxhealth)                 reciever.setHealth(maxhealth);
 else                 reciever.setHealth(healamount + reciever.getHealth());
                if (reciever.equals(sender)) {
                  sender.sendMessage("String_Node_Str");
                }
 else {
                  sender.sendMessage("String_Node_Str" + reciever.getName());
                  reciever.sendMessage(sender.getName() + "String_Node_Str");
                }
              }
 else {
                sender.sendMessage("String_Node_Str");
                if (!reciever.equals(sender))                 reciever.sendMessage(sender.getName() + "String_Node_Str");
              }
            }
          }
        }
      }
      Thread.sleep(1000);
    }
 catch (    Exception ex) {
    }
  }
}

Fixed version (ground truth):
public void run(){
  while (enabled) {
    try {
      Set<Entry<Player,Long>> set=timeStamp.entrySet();
synchronized (sync) {
        Iterator<Entry<Player,Long>> it=set.iterator();
        while (it.hasNext()) {
          Entry<Player,Long> next=it.next();
          if ((System.currentTimeMillis() - timedelay) > next.getValue()) {
            Player reciever=playerMap.remove(next.getKey());
            Player sender=recieverPlayerMap.remove(reciever);
            it.remove();
            if (sender != null && reciever != null && sender.isOnline() && reciever.isOnline()) {
              ItemStack item=sender.getInventory().getItemInHand();
              if (item.getTypeId() == itemId && item.getAmount() >= amountRequired) {
                if (item.getAmount() == amountRequired) {
                  sender.getInventory().remove(item);
                }
 else {
                  item.setAmount(item.getAmount() - amountRequired);
                }
                if (reciever.getHealth() + healamount > maxhealth)                 reciever.setHealth(maxhealth);
 else                 reciever.setHealth(healamount + reciever.getHealth());
                if (reciever.equals(sender)) {
                  sender.sendMessage("String_Node_Str");
                }
 else {
                  sender.sendMessage("String_Node_Str" + reciever.getName());
                  reciever.sendMessage(sender.getName() + "String_Node_Str");
                }
              }
 else {
                sender.sendMessage("String_Node_Str");
                if (!reciever.equals(sender))                 reciever.sendMessage(sender.getName() + "String_Node_Str");
              }
            }
          }
        }
      }
      Thread.sleep(1000);
    }
 catch (    Exception ex) {
    }
  }
}