.pof file can't work

hi.

i just got a piece of DE2 board,there is a question when i do the exercise follow the <Quatus II Introduction Using Verilog Design>, if i use the JTAG mode to programming and configure ,it's ok,

at the AS mode ,i do like the follw steps:

1.assignments > device > device and pin options > configuration >chose EPCS16 > compile

2.tools > programmer > make sure the hardware setup is

usb_blaster and the mode is active serial programming,add the .pof file ,check program/configure, > start

3. i turn off the power , check the run/prog switch back to run site,then turn on the power,but the board doesn't look like work normal .

4. i have try to use the "conver programming file"the generate the .pof file by the .sof file. then , use this file do it again,it works.

i don't why? all steps are follw the doc.my quartus II is 9.1 web edition .