At the end I did the following things:
1) disable ATI/AMD drivers
2) add script @ http://thecodecentral.com/2011/01/18/fi ... orking-bug
, using "step 2" (not step 2 old)
3) in the previous script, modify line DRIVERS="ehci xhci" using ehci_hcd & xhci_hcd as commented in the script itself (since I had no ehci folder but ehci_hcd) --> not sure this is really needed.
4a) edit (as root) /etc/default/grub and put
(by default was empty ie. "")
4b) run in a root-console 'sudo update-grub'.
Still same error in sleep.log but everything works perfectly.
Hoping this can help.