There is a small folder inside the minecraft/bin folder called natives. This folder contains files that have platform-specific code. When you copied over your install, you copied over the Windows-native files in this folder. As a result, the game fails to run.
You can fix this by replacing the contents of that folder with the correct files from a valid 1.4.6 installation that was done on a Mac.
I'm not entirely certain how you can do that, but the files from a 1.4.7 install may work if in fact Mojang have not changed very much except for some classes in the main jar file. Archive your modded install somewhere else, install MC 1.4.7 fresh, and save the natives folder it generates somewhere convenient. Wipe the rest and put your modded install back in place, remove its Windows-based natives folder, and drop in your new one. See if it runs.
If using a 1.4.7 natives folder doesn't work though, one way to try would be to use Minecraft Nostalgia, which can downgrade the latest version of Minecraft to an arbitrary previous version. (I've used it for downgrading to 1.2.5 for modding purposes, but I haven't done it on a Mac. It appears to support Win/Mac/Linux though.)
You would safely archive your modded install, wipe it from the minecraft/ folder, then run the vanilla launcher to get 1.4.7. Close it out, then run Minecraft Nostalgia, choosing 1.4.6 from the list. Once it's done the conversion, grab the minecraft/bin/natives folder for later. Wipe the rest, put your modded install in, and delete the minecraft/bin/natives folder that came from Windows. Finally, drop in your natives/ folder gleaned from MC Nostalgia, cross your fingers, and launch!
Again, I've never had to do this, but it should work.
If I understand your question correctly, you'll probably want to reset the game. Warning: If instructions aren't followed correctly, all worlds will be deleted. I am not responsible if this happens.
- For Windows 7, press start (on Windows XP click "run..." afterwards and then type in
%appdata% in the run dialog, not the search), type in %appdata% in the search bar, and press enter. A folder should pop up.
- Navigate your way to .minecraft/saves/. Copy everything in that folder to another location. Your desktop, for instance.
- Now, go back up the folders and delete the .minecraft folder. Empty your recycle bin.
- Open up the Minecraft Launcher and log in. If you followed directions correctly, it should automatically update.
- Now, close Minecraft and copy the stuff you copied to your desktop back into .minecraft/saves/
- Open Minecraft. Enjoy!
If this doesn't work, then there could be something wrong with your video card or drivers.
Best Answer
As people said in the comments, you could check:
Your technical parameters. Graphics card, RAM, processor, Disk memory
If you have any software problems. Outdated Java, too old Launcher or OS - do you run the game Fullscreen?
If you have misdownloaded/not properly updated Minecraft. You could try reinstalling Minecraft (the Launcher too).