Unity 3d frozes when loading or closing project

Occasionally I encounter issue which prevent me from closing Unity 3d or loading new project. After googling I found out that there is a process abd.exe running in the background that cause Unity to behave oddly. If your project is set up to Android project you are likely to have this process running.
More info about adb process can be found here : http://www.file.net/process/adb.exe.html

Simply saying adb is one of the Android SDK processes.

Shut all adb process from task manager panel and that should fix the problem.