SAM-BA operation failed

yes, bossac is recognising the SAM. i receive this log:

C:\Users\HP\Desktop\arduino-1.5.2\hardware\tools>bossac.exe  --port=COM15 -U false -i
Device       : ATSAM3X8
Chip ID      : 285e0a60
Version      : v1.1 Dec 15 2010 19:25:04
Address      : 524288
Pages        : 2048
Page Size    : 256 bytes
Total Size   : 512KB
Planes       : 2
Lock Regions : 32
Locked       : none
Security     : false
Boot Flash   : false

i tried to upload the bin file through bossac, but it always returns me SAM-BA operation failed when it tries to verify the flash:

C:\Users\HP\Desktop\arduino-1.5.2\hardware\tools>bossac.exe  -p COM15 -U false -
e -w -v -b dbGlove_blue.cpp.bin -R
Erase flash
Write 28512 bytes to flash
[==============================] 100% (112/112 pages)
Verify 28512 bytes of flash
[                              ] 0% (0/112 pages)
SAM-BA operation failed