Micrium Rtos - OSTimeDly not working

[nimaaa]

Hi
I have initialized the Micrium Rtos and there is no error when I compile the project but there is a OSTimeDly function in my code that is not working.
I should notify that when I give the first argument of this function ( related to number of ticks to specify the time delay ) the value of 0 , my task is working well but giving any value to this argument (500 in my code) , stops the program .

here is mu code :

#include <GPIO_LPC17xx.h>
#include <app_cfg.h>
#include <os.h>

static			OS_TCB		AppTaskStartTCB;
static			CPU_STK		AppTaskStartStk[1000];
static 			void 			AppTaskStart(void *p_arg);

int main(void)
{
	OS_ERR err;
	
	
	GPIO_SetDir(0,20,GPIO_DIR_OUTPUT);
	GPIO_PinWrite(0,20,1);
	OSInit(&err);
	if (err !=OS_ERR_NONE) {
		GPIO_PinWrite(0,20,0);
	}
	OSTaskCreate((OS_TCB		*)&AppTaskStartTCB,
							(CPU_CHAR		*)"App Task Start",
							(OS_TASK_PTR)AppTaskStart,
							(void 			*)0,
							(OS_PRIO		 )5,
							(CPU_STK		*)&AppTaskStartStk[0],
							(CPU_STK_SIZE)1000/10,
							(CPU_STK_SIZE)1000,
							(OS_MSG_QTY  )0,
							(OS_TICK		 )0,
							(void			  *)0,
							(OS_OPT			 )(OS_OPT_TASK_STK_CHK  |  OS_OPT_TASK_STK_CLR),
							(OS_ERR			*)&err);
							
	if (err !=OS_ERR_NONE) {
		GPIO_PinWrite(0,20,0);
	}						
	OSStart(&err);
	if(err !=OS_ERR_NONE){
		GPIO_PinWrite(0,20,0);
	}
}
static void AppTaskStart (void *p_arg)
{
	OS_ERR err;	
	p_arg = p_arg;
	CPU_Init();
	GPIO_PinWrite(0,20,0);
	while(1)
	{
		[B]OSTimeDly((CPU_INT16U	)	500,[/B]
							(OS_OPT			)	OS_OPT_TIME_DLY,
							(OS_ERR		 *)	&err);
		GPIO_PinWrite(0,20,1);
		OSTimeDly((CPU_INT16U	)	500,
							(OS_OPT			)	OS_OPT_TIME_DLY,
							(OS_ERR		 *)	&err);
		GPIO_PinWrite(0,20,0);
	}
}

Please help me to solve this problem.
Thanks in advance