R'ingTFM and calling the hot-line, the answer is perhaps the emergency battery is empty, either this or... I'll have to change the mother-board >o/. The hot-line says to have the puter sent to them for checking, for... 2 or 3 weeks. Aaaarrgh! Unfortunately the Bios Setup "advanced" section gives a warning about possible wrong values in IDE configuration, which could mean the mother-board. Ouch. Yet a restoration point at an earlier date (before the problem started) gives the same values and warning.
Another manual (for a slightly different model) advises to keep the laptop on main supply for 48 hours (keeping it turned off, I suppose) to reload the emergency battery. I'd be happy if this could confirm the origin of the problem before I part with my lappy for so long a time...
Does anybody had this kind of problem with her/his laptop? Please?
BTW, if any of you received a mail from me with a wrong date, it was before I found out about the problem, sorry.