DMA and USART error during transmission

Hello,

Here is my DMA and USART configuration:(BaudRate=2250000)

DMA_InitTypeDef DMA_InitStructure;	
	NVIC_InitTypeDef NVIC_InitStructure;
	
	RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);
	
	NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2);
	NVIC_InitStructure.NVIC_IRQChannel = DMA1_Channel3_IRQn;;
	NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1;
	NVIC_InitStructure.NVIC_IRQChannelSubPriority = 2;
	NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
	NVIC_Init(&NVIC_InitStructure);		
	
	DMA_ClearFlag(DMA1_FLAG_TE3|DMA1_IT_TC3);
	DMA_Cmd(DMA1_Channel3, DISABLE);
	
	DMA_DeInit(DMA1_Channel3);
	DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)&USART3->DR;
	DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)Buffer;
	DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC;
	DMA_InitStructure.DMA_BufferSize =sizeof(Buffer);
	DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
	DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
	DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;
	DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte;
	DMA_InitStructure.DMA_Mode = DMA_Mode_Circular ;
	DMA_InitStructure.DMA_Priority = DMA_Priority_High;
	DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
	DMA_Init(DMA1_Channel3, &DMA_InitStructure);
	
							
	DMA_ITConfig(DMA1_Channel3, DMA_IT_TC, ENABLE);
	USART_DMACmd(USART3, USART_DMAReq_Rx, ENABLE);
	DMA_Cmd(DMA1_Channel3, ENABLE);	
	DMA_ITConfig(DMA1_Channel3,DMA_IT_TE,ENABLE);

void DMA1_Channel3_IRQHandler(void){ // USART3_RX
 
	///	Error->1 Ok, 0 Not ok, 3 CRC, 2 Page
	
 
	
	if(DMA_GetITStatus(DMA1_IT_TC3) == SET)
	{							
						DMARead=1;
						DMA_ClearITPendingBit(DMA1_IT_TC3);
						USART_Cmd(USART3,DISABLE);
						USART_ITConfig(USART3,USART_IT_RXNE,DISABLE);
						USART_DMACmd(USART3, USART_DMAReq_Rx, DISABLE);
						DMA_Cmd(DMA1_Channel3, DISABLE);
			
		}
 
 
	if(DMA_GetITStatus(DMA1_IT_TE3) == SET)
	{
		USART_Cmd(USART3,DISABLE);
		DMA_ClearITPendingBit(DMA1_IT_TE3);
		DMA_ClearITPendingBit(DMA1_IT_TC3);
		USART_DMACmd(USART3, USART_DMAReq_Rx, DISABLE);
		DMA_Cmd(DMA1_Channel3, DISABLE);
	}

I Enable my DMA during my program to have a control on the transmission an other task. My problem is when the USART or DMA has an error DMA stop working( it works for many cycles but it stop working after some minutes). As I checked the DMA1_IT_TE3 Flag I didn't any error on the DMA. I think maybe USART has an error ( Overrun or ....). I need to find out where the error is and How I can find the usart problem when I am using DMA. In addition, How can I reset the value of DMA buffer before starting it?