Today I was using my (old) Compaq laptop where Lubuntu is regularly installed on a partition. Suddenly, it stopped to respond to any inputs, so I (wrongly?) decided to restart the system.
After the logo Lubuntu had shown in the end of the booting process, the screen went black, the line
Stopping System V runlevel compatibility
showed and the two following messages
Asking for cache data failed
Assuming drive cache: write through
repeatedly appeared. My laptop was stuck there and the operating system did not start.
I have been looking for some advice on the Internet during this afternoon, especially here on askubuntu.com, but it seems sadly that nobody has encountered exactly the same type of error. I am still working on that. If you have any ideas, please reply to this post.