When does empathy become a liability? Should the boss be involved in employees' personal problems?

Never dont think the boss can involove in individual but,in certainy cases msy happend to save his staff as friebd not bosd

In my view, empathy is never a liability. It helps to transcend boundaries between individuals. It builds trust and also provides insight to an individuals point of view, outlook, how they are willing to overcome (or not) the issues they face. Expressing an honest opinion and guidance are likely ways forward. Over a period of time, it will become clear as to whether the individual is determined enough to turn the tide or vice versa..

Unless the employee expresses his/her desire for the boss's involvement, dont think the boss should be involved. 

Trust this helps.