Custom World Won't Load in 14w17a

I made a custom world in the latest snapshot and it simply WILL NOT load even when I restarted the launcher! When I loaded my customized mushroom island world, I got a dirt screen saying "Converting World" for more than 10 minutes! After restarting the launcher and loading the world again, I got a dirt screen saying nothing! If it is related to the problem, I am running a Windows 8 PC with a Quad Core AMD A8 APU, and I have 4 GB of RAM dedicated to the game. This can normally generate an amplified world in under two seconds. Please help with this issue.
Thanks
-DarkLight (Liam Holcomb)