Can't update firmware PC 6224

Hi,

Power Connect 6224 firmware 3.3.7.3.

I'd like to upgrade to 3.3.10.3; I followed the upgrade procedure by copy tftp://my_tftp_serv/PC6200v3.3.10.3.stk image

The copy ended with no error, but sh ver returns both image1 and image2 the same (3.3.7.3).

I tried to upgrade by http interface with same result, no-error but can't see anywhere the 3.3.10.3 version.

What's wrong ?

Thank's.

Regards.

Fred.