Dock Auto-hide not working in Mac OS X Lion

In my computer I am facing problem with the Dock. I have MAC OS X lion operating system and I have set my Dock to auto hide. Normally dock disappears after opening any application from it but I am facing problem with it. When I open any application from dock after that it does not disappears. If I move my cursor over it at that time I start behaving normally. I don’t know what is wrong with it. I have tried to find solution on internet regarding this problem but that does not make any difference. Please help me to solve this problem.

You can solve this problem by resetting dock preferences in your computer. if you don’t know about how to reset the dock preferences then I will help you with this. First of all you have to open finder in your computer and after opening the finder you have to open Library folder. In the Library folder you have to open Preferences and from Preferences folder you have look for the com.apple.dock.plist file and then delete it. you have to also delete all the plist file with dock in the name and after deleting that file you have to restart your computer. Now after restarting your computer you have to check whether dock is working properly or not? I am telling you this because I was also having similar problem with the dock and after that I have deleted all the dock preference file from my system and then when restart my computer at that time i was not facing same problem. If you need any more help regarding this then let me know.

Thank you for helping me. After looking at your solution I have opened preferences folder and then removed all the dock preferences files and then I have restarted my system. After restarting the system I am not facing any issues with the auto hide option,