I have a few recently acquired cattleyas where, unfortunately, a new growth has turned brown and died. I suspect that this is due to the fact that I slacked off on watering them for a couple weeks and the new growths didn't get enough water and the plants aborted the growth. I grow outdoors and plants dry out much more quickly. Does this sound like the cause? I don't see any signs of disease on the rest of the plant.
It is likely a pythium or brown rot infection.
Extremely difficult to cure and can spread to other plants.
Isolate this particular plant.
I would then wait and see what happens to another new growth and if it is the same scenario
How do the psuedobulbs look? If the newest psuedobulbs are wrinkled it may be dehydrated. Fungus can also cause new growths to turn brown like Eyebabe said. Cattleyas like to dry out between waterings but they also need water when they are in active growth. Two weeks without water won't hurt the plant in the winter when it's not growing but when it's in active growth I would water it more often. My catts are in hydroton which dries in a few hours. I water twice a week during the spring and summer and once a week during the winter.