Hi Helen--what kind of orchid is it? Is there any kind of label in the pot? If so, what does it say?
Many orchids are deciduous, losing their leaves on old growths just before putting out a new growth spurt, but it's going to be hard answering your question without some kind of reference to the type of plant, or a picture of it, if you have a digital camera and can post one. (That would be best, actually....)