Minecraft – How to i summon an ender dragon so it won’t break blocks

Are you running the 32-bit version of Java? If so, download and install the 64-bit version. 32-bit Java has a fairly low limit set on the amount of memory it can allocate.

This will only work if you're running a 64-bit operating system though.

If that's not the issue, try to post the crash log if you can. If you're using mods and have ModLoader installed, take a look at the modloader.txt file in your .minecraft folder right after a crash. Specifically, the lines near the end of the file. It could shed some light on your problem.

Yes, they can. I've gone into dangerous mines many times, thinking my dogs were safe and sound in my home, when I see one of them randomly teleport into the lava pit in front of me. To remedy it, (here comes the solution part) I usually make the dogs sit down because after that they won't move. At all. It's absolutely perfect for going to my obsidian mine, situated ON AN ACTIVE LAVA LAKE, home to the graves of many dogs.