First, let's put "low morale" in realistically practical terms: Low morale = people not positively engaged with their work. There are a few typical types of "low morale" employees.
Passionately Destructive – eradicate immediately and stop the bleeding; fire these people (terrorists)
Actively Repelled – determine source of their anger; look for themes in their specifically cited examples, as these examples will rarely paint a picture of the entire problem.
Passively Disengaged – as manager, look to your own reaction to their feelings; incredulity is likely to be met with opposing incredulity by your employee. A manager's responding with helplessness will result in employees also feeling helpless. Ardent determination on the manager's part will be met with either similar determination, or your perception of reality will be rejected by your employees, and you will lose further credibility.
Keys to managing employee morale are to first and foremost understand yourself, and secondly, you must understand your employees, and what motivates them. Are they positive motivated people, who are driven by goals, success, and achievements? Or are the negatively motivated people, those who are motivated by fear of being fired, of not being able to pay their energy bills, of being disappointing their family/friends?
Learn about yourself and about what motivates your employees (along with discovering the roots of their discontent), and manage/motivate accordingly.