I have a serious problem about Unity 2.6.1 and Unity 3.
I want to run unity3 or Unity 2.6.1 and clicked Unity's icon but Unity does not work. I am not getting an error. Windows mouse icon change as waiting but unity does not open.
How can i resolve this problem?
Try to press cntrl or alt (don't remember which) as you click on the Unity icon.
I recently had this issue and to fix it I had to add a DEP (Data Execution Prevention) exception for the unity editor. Assuming windows 7, follow this link http://www.itechtalk.com/thread3591.html and choose the executable in program files/unity/editor/unity.exe.
If your using a 64-bit OS, go to Program Files (x86) instead.
I have the same problem with my version :(