rb750g doesn't work after upgrade to 4.9

Hi,

i have rb750g,
i tried upgrade router OS from version 3.5 to version 4.9
I uploaded it in the root directory, via winbox, and restarted router
Now router always fails to start and network ports disable and enable again after less then a minute..
Reset button doesn’t solve..

Do you have some ideas?

i posted this in right place, now

thanks
daniele

Try to netinstall >> http://routerboard.com/pdf/123/rb750GmA.pdf