Originally Posted by frostbite
MS Word seems to be fond of doing that too, if you're not ultra careful just prior to committing to print.
At least with Word you can try to control it by going to Format -> Paragraph -> Line and Page Breaks (tab) and then using some combination the Widow/Orphan control, Keep lines together and Keep with next options.
Their operation may seem totally random and unpredictable, but at least there will always be some combination that stops the single line appearing on its own at the very end of the document.