My son's latitude crashed right after college mid-terms. It took us two weeks to finally get a CMOS battery, put it in, and find THE SAME MESSAGE on the screen (time of day clock stopped). What worked for us was to pull out the bar battery, CMOS button battery, and unplug the cord. We let it sit for 10 mins. then came back and hit the power button for count of 10. Then the batteries, and cord went back on, and powered-on and (Hooray!!) we were back in business. Apparently the little bit of stored battery power in these batteries keeps the laptop from completely discharging and by hitting the power button for 10, that did it. Next you will be told to update your time.
Hope this helps you!