I've been playing Minetest for a while now, but I've never come across this problem until now. Any time I create a new world, the map starts generating normally for about a minute, but then it just stops. At times, it appears to be generating very slowly. I haven't done anything different. I tried downloading Minetest 0.4.9-stable from the Linux Mint 17 software manager AND downloading and compiling the source code from Github (Minetest 0.4.9-dev). Same result. I don't know what else to do. Any help would be GREATLY appreciated!
Here's a screenshot of the problem: