Error Type: Error occurred in deployment step 'Recycle IIS Application Pool': The vssphost4.exe process was unable to start due to an unknown error

I got the following error while deploying sharepoint 2010 visual wepbart

"Error occurred in deployment step 'Recycle IIS Application Pool': The vssphost4.exe process was unable to start due to an unknown error or problem."

The reason for this error is There is one more visual studio is opened and its debugging location is same as the currently running visual studio debugging location.

Solution is close all opened visual studio and reopen your project and deploy. now you wont get any error.