Bossa / SAM-BA cannot find device - CDC looks OK

[SadE]

Hi,

I have a board with a SAM7S64 with USB and I'm trying to use the rom bootloader to flash my application.
I first put pull high the TST pin
Plugged usb
Wait 1 min
Removed usb,
Removed TST jumper,
then put ERASE jumper,
Plugged USB ,
Wait 1 minute
Removed USB

After this cycle I can get the BOSSA CDC driver on my system (Win 7 64bits).
The problem is that bossac cannot found device .
SAM-BA just hang of switch off as soon as I click on CONNECT
If I'm trying to send V# to get version using a terminal I got nothing.

I cannot see what's wrong here because if CDC is correctly enumerated , I guess the bootloader is running no ?