They are a bit temperamental, it has to be said - what they hate is the change of season and draughts, they abhor draughts. So when it turns from winter to spring, they drop leaves, when it turns from autumn to winter, they drop leaves - mostly cos the environment changes - we put the heating on, we turn it off. Find somewhere out of draughts, away from heat sources, with a good light (winter sun won't hurt it at all, it's spring/summer/autumn sun that damages) in a place where the temperature doesn't have dramatic changes between, say, night and day (so not in the lobby where your front door is, for instance) Feed it with something like Baby bio once a week - you may need to trim it back in the spring if it survives, it might be quite twiggy looking by then. Allow the compost to dry out a bit between waterings, don't leave it sitting in water, talk to it, or at least, breath on it frequently! Not shouting and cursing, gently and kindly, please! And if you're really desperate, play it some Mozart - I'm not joking either - plants respond well to Mozart, believe it or not.
If you do prune it back, stand it on newspaper or something - they tend to bleed a lot of white milky sap.

I would say the problem is it's room temperature and the dry air. Try watering from the bottom, leaving a small amount of water in a container underneath, setting it up on pebbles will also help.

I've got one, DocBob, had it 6 years, it's now about 4 feet high in its pot and 3 feet wide - I follow the rules I've laid out above - in fact, I think I might have to prune in the spring because its getting too big...

Yes it is the environment as you have pointed out. I have worked with many of these, in Hydroponics in large open-planned offices. They dislike cigarette ends and cups of cold coffee.

ha ha, bet they get a lot of those in offices...

one advantage of being in a big office is that it has a lot of people breathing on it all day and at night when they don't want that every one has gone home.