schmuel,
It looks like you're using a lead-free device. The flash programmer doesn't....yet, support these devices.
You need to save the following text to <nios2_install>/bin/nios2-flash-override.txt:
# EPCS1N (lead-free)
sector_size = 32768
sector_count = 4
# EPCS4N (lead-free)
sector_size = 65536
sector_count = 8
Please report back with any further issues that you have.
Cheers,
- slacker
[UPDATED]: Though I'm not sure, you may have to modify the HAL flash abstraction commands....if you have a need to access the flash from your software.