AVRdude weird fuses error

hi all!

i am trying to burn a combined firmware on my mega's 16u2. i am using: windows 8 arduino uno a isp avrdude (i can't use flip since i dont have dfu firmware)

the command i am running:

avrdude -p at90usb162 -F -P com4 -c arduino -U flash:w:MEGA-dfu_an d_usbserial_combined.hex -U lfuse:w:0xFF:m -U hfuse:w:0xD9:m -U efuse:w:0xF4:m - U lock:w:0x0F:m

avrdude output is:

avrdude: AVR device initialized and ready to accept instructions

Reading | ################################################## | 100% 0.01s

avrdude: Device signature = 0x1e950f
avrdude: Expected signature for AT90USB162 is 1E 94 82
avrdude: NOTE: FLASH memory has been specified, an erase cycle will be performed

         To disable this feature, specify the -D option.
avrdude: erasing chip
avrdude: reading input file "MEGA-dfu_and_usbserial_combined.hex"
avrdude: input file MEGA-dfu_and_usbserial_combined.hex auto detected as raw bin
ary
avrdude: writing flash (16384 bytes):

Writing | ################################################## | 100% 3.45s

avrdude: 16384 bytes of flash written
avrdude: verifying flash memory against MEGA-dfu_and_usbserial_combined.hex:
avrdude: load data flash data from input file MEGA-dfu_and_usbserial_combined.he
x:
avrdude: input file MEGA-dfu_and_usbserial_combined.hex auto detected as raw bin
ary
avrdude: input file MEGA-dfu_and_usbserial_combined.hex contains 16384 bytes
avrdude: reading on-chip flash data:

Reading | ################################################## | 100% 3.09s

avrdude: verifying ...
avrdude: 16384 bytes of flash verified
avrdude: reading input file "0xFF"
avrdude: writing lfuse (1 bytes):

Writing |                                                    | 0% 0.00s ***faile
d;
Writing | ################################################## | 100% 0.08s

avrdude: 1 bytes of lfuse written
avrdude: verifying lfuse memory against 0xFF:
avrdude: load data lfuse data from input file 0xFF:
avrdude: input file 0xFF contains 1 bytes
avrdude: reading on-chip lfuse data:

Reading | ################################################## | 100% 0.01s

avrdude: verifying ...
avrdude: verification error, first mismatch at byte 0x0000
         0xff != 0x00
avrdude: verification error; content mismatch

avrdude: safemode: lfuse changed! Was ff, and is now 0
Would you like this fuse to be changed back? [y/n]

what is happening? what are those fuses? i have no clue how to fix it, if anyone here encountered this before help would be very appriciated!

i tryied connecting a 100uf capacitor between reset and ground on my uno.. nothing seems to help.

i have no idea what could be the problem. ive been researching for days and still cant figure out what to do.

thank you for taking the time to read my post!

tali