Lpc2000

I am trying to program a Flash device, SST39VF1601, via the UART. 
The flash programmer is OK, and I can also write the first few 
instructions into the device. But just after that, it stopped 
working. I have tried many times, however, the results were the same.
The following were the several lines in HEX form that could be 
written into the flash:

:2000000018F09FE518F09FE518F09FE518F09FE518F09FE5805F20B9F0FF1FE518F0
9FE5ED
:200020008C0000804000008044000080480000804C00008000000000000000005000
0080CC
:20004000FEFFFFEAFEFFFFEAFEFFFFEAFEFFFFEAFEFFFFEA0E00A0E1D3F021E3B4D0
9FE5C4

And the corresponding instrutions are:
_start:	ldr pc, ResetAddr				
	ldr pc, UndefinedAddr			
	ldr pc, SoftwareAddr			
	ldr pc, PrefetchAddr			
	ldr pc, DataAbortAddr				
	.word   0xb9205f80				
         ldr pc, [pc, #-0xff0]			
	ldr pc, FastAddr

ResetAddr: 	.word ResetInit
UndefinedAddr:	.word Undefined
SoftwareAddr:	.word SWI_Handler
PrefetchAddr:	.word PrefetchAbort
DataAbortAddr:	.word DataAbort
Non_Used:		.word 0
InterruptAddr:	.word 0
FastAddr:		.word FIQ_Handler

Undefined:						
	b Undefined
SWI_Handler:
	b SWI_Handler
PrefetchAbort:
	b PrefetchAbort
DataAbort:
	b DataAbort
FIQ_Handler:
	b FIQ_Handler


/* Initialize the stacks for each mode */
StackInit:
	mov	r0, lr
/* build the SVC stack */
	msr	cpsr_c, #0xd3
	ldr	sp, =_svc_stack  /*_svc_stack is defined in link 
the file*/

24 instuctions in total; It's at the last one that the programmer 
stopped. 

What's the problem? Hopefully someone could help me?

Thanks in advance!

Best regards,

Kevin