Minecraft not opening how do I fix?

After installing Minecraft 1.7.4 on my new Mac Version: 10.6.6 I clicked play in the launcher and the it opened but only for a few seconds before closing, How do I fix?
-I tried re-installing
-The workbench icon is very pixelated (more than the launcher) for some reason
-Update 1.7.4 on a MacBook Pro

Backup all you need from the.minecraft folder and delete the folder and the launcher. Erase them from them from your Recycle Bin as well. Download Minecraft again from minecraft.net

Hope it works!