STM32F103ZE USART1 interrupt issue

Hi,

#include <
stm32f10x_nvic.h
>
#include <
stm32f10x_gpio.h
>
#include <
stm32f10x_rcc.h
>
#include <
stm32f10x_flash.h
>
#include <
stm32f10x_usart.h
> 
#define MAX_STRLEN 10 
volatile char received_string[MAX_STRLEN+1];
void USART1_Initialization(void);
void USART_Puts(USART_TypeDef* USARTx, volatile char *s);
void USART1_IRQHandler(void);
//********** USART1 INITIALIZATION **************
void USART1_Initialization(void)
{ 
// ******** RCC Config **************
RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1,ENABLE); // Enables clock for USART1
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA,ENABLE); // Enable clock for port A

// ******** GPIO Config **********
GPIO_InitTypeDef GPIO_InitStructure;
// Configure USART1 Tx (PA.09) as alternate function push-pull 
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9; 
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; 
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP; 
GPIO_Init(GPIOA, &GPIO_InitStructure); 
// Configure USART1 Rx (PA.10) as input floating 
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10; 
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING; 
GPIO_Init(GPIOA, &GPIO_InitStructure);
// ********* NVIC Config ***********
NVIC_InitTypeDef NVIC_InitStructure; // Configure the NVIC (nested vector interrupt controller) 
#ifdef VECT_TAB_RAM 
NVIC_SetVectorTable(NVIC_VectTab_RAM, 0x0); // Set the Vector Table base location at 0x20000000 
#else // VECT_TAB_FLASH
NVIC_SetVectorTable(NVIC_VectTab_FLASH, 0x0); // Set the Vector Table base location at 0x08000000
#endif 
NVIC_PriorityGroupConfig(NVIC_PriorityGroup_0);
NVIC_InitStructure.NVIC_IRQChannel = USART1_IRQChannel; // we want to configure the USART1 interrupts
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0; // this sets the priority group of the USART1 interrupts
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0; // this sets the subpriority inside the group
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; // the USART1 interrupts are globally enabled
NVIC_Init(&NVIC_InitStructure); 
// ******** USART Config **********
USART_InitTypeDef USART_InitStruct; // this is for the USART1 initilization
USART_InitStruct.USART_BaudRate = 9600; // the baudrate is set to 9600
USART_InitStruct.USART_WordLength = USART_WordLength_8b; // want the data frame size to be 8 bits (standard)
USART_InitStruct.USART_StopBits = USART_StopBits_1; // want 1 stop bit (standard)
USART_InitStruct.USART_Parity = USART_Parity_No; // don't want a parity bit (standard)
USART_InitStruct.USART_HardwareFlowControl = USART_HardwareFlowControl_None; // don't want flow control (standard)
USART_InitStruct.USART_Mode = USART_Mode_Tx | USART_Mode_Rx; // enable the transmitter and the receiver
USART_Init(USART1, &USART_InitStruct);
USART_Cmd(USART1, ENABLE); // enable USART1 peripheral
USART_ITConfig(USART1, USART_IT_RXNE, ENABLE); // enable Receive Data register Not Empty interrupt
USART_ITConfig(USART1, USART_IT_TXE, ENABLE); // enable Transmit Data register Empty interrupt
}
//************ USART_PUTS FUNCTION **********
void USART_Puts(USART_TypeDef* USARTx, volatile char *s)
{
while(*s)
{ 
while( !(USARTx->SR & 0x00000040) ); // wait until data register is empty
USART_SendData(USARTx, *s);
*s++;
}
}
//******** USART1_IRQHandler *************
void USART1_IRQHandler(void) 
{
static unsigned int cnt = 0; // counts number of characters
unsigned int i;
if(USART_GetITStatus(USART1, USART_IT_RXNE)) // check if the USART1 receive interrupt flag was set
{
char t = USART1->DR; // character from data reg is stored into t
if (t != '\r') // if not CR (carriage return)
{ 
received_string[cnt] = t; // character is stored into receive buffer
cnt++; // increase number of character
}
else // if there's no more characters
{
received_string[cnt++] = '\0'; // put terminator character in the end of buffer
cnt = 0; // reset character counter
USART_Puts(USART1, received_string); // send character to printing
for (i = 0; i <= MAX_STRLEN+1; i++) // flush buffer
received_string[i] = '\0'; 
} 
}
}
//*********** MAIN FUNCTION ************
int main(void) 
{
NVIC_SETPRIMASK(); // Disable ALL interrupts 
USART1_Initialization(); // Initialization of all parameters and enabling USART1 interrupt
NVIC_RESETPRIMASK(); // Enable ALL interrupts
USART_Puts(USART1, ''Welcome \r\n''); // just send a message to indicate that it works
while(1)
{ 
// waiting for USART1 interrupt to occur
}
}