program stops working

when approx. half a page of work is typed the icons start flashing and the work cannot be saved and Libra will not respond. The work cannot be retrieved. I have spent hours on work that has been lost!

The work cannot be retrieved. I have
spent hours on work that has been
lost!

LO should be auto-saving your work on a fairly regular basis, unless you have turned that off in Options. The next time you open LO is should attempt to recover the file.

But you should periodically be hard-saving your work manually as well. Too many things can happen on a computer to risk losing that kind of time.

As for the problem, OS and LO version would be helpful, as well as more detail.