Problem in Jailbreaking Iphone 3g [cant DFU iphone]

I hope someone can help me with this problem...Iphone 3g which i tried to update from 2.2.1 into 3.0....first i connect it to i tunes and do the restore process and everything went well.Next step is to do Jailbreak with the use of redsnow 0.72 and 0.8 but all failed..the problem is the phone wont go into DFU mode.although i followed the steps carefully in redsnow but still the phone wont goto DFU mode and instead it goes to recovery mode...Take note this is not the first time i JB or unlocked iphone 3g,3gs,ipod touch but this unit is different from the rest...it just wont goto DFU mode..i already changed cable,changed port and tried with other pc but still same status...can anyone help me with this problem?btw i have inserted image to show the error...thanks in advance...already tried using new version of redsnow but still same problem.cant put iphone to DFU mode...also checked home and power button and no problem..............

http://img195.imageshack.us/img195/599/ipon.jpg

Check this forum. Another user (yesterday I think) had a problem with his Power Button so he could not get into DFU.

He goggled a little an found a way of doing that with SW. Maybe that can help you.