What's happened to my Cactus?

[sarahq03]

It has been raining here in San Antonio for the past week. My lovely little cactus was doing so well, even had a pink flower.
Now there's all these black stalactite looking things growing off the top.
What is this? If it's bad what do I do, can I save my Cactus?
There are also ants piling into the drainage hole at the bottom of the container and they seem to be everywhere.