This is what appears when i launched 1.7.2
^java.lang.NullPointerException
at net.minecraft.launcher.GameLauncher.getMinecraftArguments(GameLauncher.java:479)
at net.minecraft.launcher.GameLauncher.launchGame(GameLauncher.java:422)
at net.minecraft.launcher.GameLauncher.onDownloadJobFinished(GameLauncher.java:690)
at net.minecraft.launcher.updater.download.DownloadJob.popAndDownload(DownloadJob.java:124)
at net.minecraft.launcher.updater.download.DownloadJob.access$000(DownloadJob.java:15)
at net.minecraft.launcher.updater.download.DownloadJob$1.run(DownloadJob.java:94)
at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source)
at java.util.concurrent.FutureTask.run(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)^
Please attach the complete output of the "Development console" which can be found on the second tab of the launcher.
If the launcher closes after game start, please edit your profile and select "Launcher visibility" then, "Keep the launcher open".
Also, your description says 1.7.2 but your bug shows 1.7.4. Which is it?