Remote update Cyclone IV from EPCS

Hello.

I have DE2-115 and i'm able to reconfig it from EPCS with NIOS.
But I have some problems with factory image.

My factory image takes addresses in EPCS from 0x0 to 0xF0000. (Sectors 0 - 15)
NIOS II erase sectors from 0 by 15. After it NIOS II is writing image to EPCS.
After Power Up everithing is fine. FPGA reconfigured from EPCS.

In next step i'm erasing sector number 16.(It was empty.)
After Power Up FPGA didn't reconfigure from EPCS.

What's going on? Is it going on because changes epcs status register?
Am i moving in the right direction?