When you ht the expand button to expand the window, it crashes my entire computer
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Unable to replicate.

It is very unlikely it crashed your entire computer which tells me that it isn't directly an issue with the launcher. If you can replicate, comment below and I will reopen.

Hi, I am seeing a similar issue with one of my two Macs. I have a MacBook Pro running Mac OS 10.8.4 which is NOT affected, but my iMac 3.6GHz Intel Core i5 OS 10.7.4 is reproducible 100% of the time. However, my entire computer doesn't crash, in fact the Launcher remains open, but the spawned Minecraft application closes hard, so maybe I should open a new issue. To reproduce, open the Minecraft Launcher, then press the Play button. While Minecraft is opening (it takes a few seconds), click the green "maximize" button. It crashes every time on my iMac. If you wait and let the black screen pass, splash screen load, and main "Singleplayer/Multiplayer..." menu appear, it does not occur. It has to be in the first four or five seconds while the application is starting. The Apple error reporter appears after the crash, but aside from the Development Console messages, Minecraft doesn't tell me anything about what just happened.
Here's what the Development Console has to say during this time (approximate start and end due to me re-opening the application and not being sure where one attempt ends and the next starts):
YOU CAN CLOSE THIS LAUNCHER IF THE GAME STARTED OK ----
(We'll do this automatically later ;D) ----
Client> 2013-07-18 14:25:01 [CLIENT] [INFO] Setting user: ibennetch
Client> 2013-07-18 14:25:01 [CLIENT] [INFO] (Session ID is token:0760bd73afd345f29ec5145b0bf89db1:b1c59e4a24f94d5dbda1ba48bdebced5)
Client> 2013-07-18 14:25:02 [CLIENT] [INFO] LWJGL Version: 2.9.0
Client> 2013-07-18 14:25:02 [CLIENT] [INFO] Reloading ResourceManager: Default
Client>
Client> Starting up SoundSystem...
Client> Initializing LWJGL OpenAL
Client> (The LWJGL binding of OpenAL. For more information, see http://www.lwjgl.org)
Client> OpenAL initialized.
Client>
Client> Invalid memory access of location 0x0 rip=0x1160074b2
Game ended with bad state (exit code 132)
Deleting /Users/me/Library/Application Support/minecraft/versions/1.6.2/1.6.2-natives-1374171899105405000
Getting syncinfo for selected version
Queueing library & version downloads

Another similar bug was closed as a duplicate of https://mojang.atlassian.net/browse/MC-6665, you may wish to look there for more help.
Please post mac specs, as I have not encountered this problem on my Macbook Pro.