NIOSII flash downloader probelm

I use the software 8.0,quartus 8.0 and sopc 8.0,niosII 8.0.

my spoc file:3c_40.sof download in quartusII

then I use the NIOSII hardware run,the result ok

but when I want to flash the whole porject to the epcs,I meet probelm

I add an epcs cotroller in my design in the sopc builder.

the address 0x00003800-0x00003fff

and set the Rest Vector 0x00003800 offset0x0

then I use the flash programmer in command-line,make the .flash file

successfully.

I first download the sopc.sof into the fpga,then I wnat to download the flash file into the epcs,but failed.

My command:nios2-flash-programmer --epcs --base=0x00003800 hello_world_small.flash

the cmd console show:

Using cable "USB-Blaster [USB-0]",device 1,instance 0

Resetting and pausing target processor:OK

Checksummed/read 61kB in 1.7s

Erase failed at offset 50000

Leaving target processor paused

I tried in the IDE Flash Programmer ,but also failed.

why?

I use EP3C40F324I7N and EPCS4,use JTAG

and I can use the Quartus II Programmer to download other hardware porjects i