Hi
Since I last closed Unity I have a problem: When I start Unity it doesn’t show me the main window even if I create a new project or open an existing project. 
Does anyone know this problem, I’m using Unity for Mac?
Thank’s.
realm_1
try combinations of:
[apple] + 1
[apple] + 2
[apple] + 3
[apple] + 4
[apple] + 5
[apple] + 6
where [apple] is the “command” key on your keyboard with the weird little logo thingy on it. Usually on the left hand side of your space bar.
Thank you for the fast answer but only the animation window appears.
very interesting. How well do you know your mac?
I think I’ve figured out what’s happened… possibly.
If you have a multi-monitor setup somewhere in your way of working, I think you’ll find the main Unity window on that other monitor. ie if you’ve gone home with a laptop, and opened up Unity without, the Unity main window is still sitting out there, on that other screen.
If you have only one monitor, like a laptop, and never used another monitor, hunt around the left, right and bottom edges of your screen, I think you’ve accidentally moved the window mostly off the screen somewhere.
WAIT! There’s one more option I’ve found. If you’re using apple Spaces, which I am, I’ve just managed to move an open Unity window to another space by dragging it to the bottom of the screen, and still able to access the menus in the original space.
I have a MacBook Air and no other screens, I’m using spaces, but I would have found the window, if it was hidden somwhere there.
If I let all the windows appear, I think it’s called Exposé, The window title appears, but no preview image.
I’ve run out of ideas. Sorry. Have you managed to contact anyone at Unity? Their Nordic and UK offices should be open by about now.
Ok, thanks for the answers. I’ll contact them, but before I’ll try to reinstall Unity.
I solved the problem! I deleted all the Unity files in the library and it worked!
WELL DONE! How did you track it to that? And Which library: Unity Library or project library?
On another note, have you seen how quantity of cache files grow in Unity Mac with regards phsyics rigs? Mine grow oddly large very quickly, lots of physics, well, all physics in my prototype. When moving or sharing the project I get oddities if I don’t move the cache. All scripts and links to variables/objects are undone. Somehow they’re stored in that cache.
I deleted the cache of my mac. So I searched in the librery (of my mac) with the search word unity and then I deleted all diplaying files.
I havent seen yet that the cache files growing so fast up. But maybe you can delet them after running your project. How do you share your project? Do you create an unitypackage? When I do this and I dont put all the used scripts into the package it gives me the same result.
I have my project on my usb-stick so I havent got this problem. And I use for devloping mac and windows so and they are both compatible with themself without copying the cache even if I added somthing new.
Another question where is the project cache?
I just wanted to say that I had the same behavior from Unity (Mac, Version 3.3.0f4 - 63135) today and I found your solution useful.
I deleted all “unity” files in my Library and the problem was solved.
I wish we had an official answer to what could cause this though.
This morning Unity was working fine, I shut down my Mac for a couple of hours and when I tried to get back to working with Unity, it simply wouldn’t start.
I followed Andeee’s advice and deleted /Library/Preferences/com.unity3d.UnityEditor3.x.plist but the problem persisted.
I tried opening existing projects (and all scenes available in each of them), created new projects, still nothing. The top screen bar changed to Unity and it’s menus, but the Unity UI wouldn’t appear. Anyway, after deleting the unity files from my Library things work ok. Thanks realm_1.
I know this is an old thread, but this is a nasty bug and it still happened on my new work Mac running Lion, with the latest Unity just installed last Friday. The fix is easy though. Just go to Window → Layouts → pick any layout. (2 by 3, 4 Split, Tall, Wide) This will bring the window back to the default position.
I’m assuming it might not work if you set the same layout that it already was. (default is Wide) So try two different ones in this case.
I’m using multiple desktops. (expose/spaces replaced by mission control)