Gray screen when trying to open unity.

go to "C:\Users\% your user name%\AppData\Local\Unity\Editor" and see "editor.log". You can find here some details

Put this into command prompt if you have Windows 64 bit and it should let you load the project.

  "C:\Program Files\Unity\Editor\Unity.exe"  -projectPath PUT PATH HERE

If You have a different version of Windows just put the path of your unity installation instead of what is up there. If you have mac I'm sure you could find some helpful information here http://docs.unity3d.com/Manual/CommandLineArguments.html . Not sure how command arguments work on mac but I'm sure its not that different.

I am having the same issue.

Same problem is happening with me I really need to make a game and I am fed up with this so the people who work at unity should fix this right now

I am also having this issue, here's my log file

 LICENSE SYSTEM [20151215 22:43:55] No start/stop license dates set
 
 LICENSE SYSTEM [20151215 22:43:55] Next license update check is after 2015-06-29T00:12:59
 
 Built from '5.3/release/package-manager-disable' branch; Version is '5.3.0f4 (2524e04062b4) revision 2434272'; Using compiler version '160040219'
 OS: 'Windows 7 Service Pack 1 (6.1.7601)' Language: 'en' Physical Memory: 3326 MB
 BatchMode: 0, IsHumanControllingUs: 1, StartBugReporterOnCrash: 1, Is64bit: 0, IsPro: 0
 Initialize mono
 Mono path[0] = 'E:/Program Files/Unity53/Editor/Data/Managed'
 Mono path[1] = 'E:/Program Files/Unity53/Editor/Data/Mono/lib/mono/2.0'
 Mono path[2] = 'E:/Program Files/Unity53/Editor/Data/UnityScript'
 Mono config path = 'E:/Program Files/Unity53/Editor/Data/Mono/etc'
 Using monoOptions --debugger-agent=transport=dt_socket,embedding=1,defer=y,address=0.0.0.0:56472
 ListPackages failed, output: This version of E:\Program Files\Unity53\Editor\Data\Tools\nodejs\node.exe is not compatible with the version of Windows you're running. Check your computer's system information to see whether you need a x86 (32-bit) or x64 (64-bit) version of the program, and then contact the software publisher.
 
 
 InstallEditorPackages failed, output: This version of E:\Program Files\Unity53\Editor\Data\Tools\nodejs\node.exe is not compatible with the version of Windows you're running. Check your computer's system information to see whether you need a x86 (32-bit) or x64 (64-bit) version of the program, and then contact the software publisher.
 
 
 installJavascriptPackages failed
  
 (Filename: C:/buildslave/unity/build/Runtime/Utilities/Argv.cpp Line: 168)
 
 Error loading file:///Z%3A%2FUsers%2FMajor%2FAppData%2FRoaming%2FUnity%2FPackages%2Fnode_modules%2Funity-editor-home%2Fdist/index.html#/project/recent
 
  
 (Filename: C:/buildslave/unity/build/Editor/Platform/Interface/NativeWebViewWindow.cpp Line: 50)