Ok, I also setlled on reinolb's workaround: it works!!! I'll check on next d-u if I can revert.
BTW, dibl, how did you get your system details on the previous page? I need to check that I have a "discrete" Intel graphic (there is supposed to be one on this laptop and I should be able to switch it on and off as needed, to save on the battery life for example). lspci didn't tell me much about it.