hafsteinnd

Your java is outdated. Update your java.

Give us the logs

That's another feature. I like that because morphing all the time has driven me crazy. So advanced genetics is a great feature for flying.

Or more if needed

Try to add more memory to your luncher. You can do that by clicking on the sprocket in the upper right corner.

Kill a flying mob like a bat and you'll morph into it, then you should be able to flly by double tapping the space bar.

There is so many topics like this, search for the solution before you post But I think you'll need to update your java.

Give us the logs

You'll need to update your java

Are you playing on a server?

You can try to delete the mapwriter config and let it load again by starting the luncher.

Go to terminal and type in "java -version" if it tells you that you have 1.6.0 you will need to download JDK unless you change your system to JRE.

Open up your luncher and click on the sprocket (settings) in the upper right corner and press on "Logs".

Mac OS X version 10.9.2

I had the same problem. I updated java but I just downloaded jre and the luncher didn't start. So I tried to download jdk and that worked. You can change this in the Terminal if you want to use jre.