Mojang Team has been released a new pre-release, 1.7.4, to fix some crashes that some people had encountered. Minecraft 1.7.4 Official will be out on Tuesday.
To get pre-releases, open your launcher and press the “New Profile” button. Call it “snapshots” and check the box saying “Enable experimental development snapshots” and save. To switch to the normal version, you can select it in the dropdown at the bottom left corner of the launcher.