It may be a sign that you need to increase the light. My dendrobium did the same thing as they flowers were opening, but because it had enough light all of the flowers eventually turned the right side up. Since your have all bloomed, I am wondering if it doesn't have enough light to turn them. I'm also wondering if it's too late for them to turn since they appear to be very mature blooms at this point - like open for a week or so.
If you just got it not to long ago, maybe it was the change in its new growing conditions that caused it to have upside down blooms. Orchids are tempermental sometimes. Usually dends will sulk quite a bit when I buy them and take them home. So I'm just happy if I can keep one alive sometimes...lol.