Originally Posted by swiftaw
It's not my intention to be a pedant here, but this is not a valid path. You have the wrong slashes in here -- those slashes are to escape spaces without quotes. They also happen to be Windows' directory dividers, but that's beside the point. The correct path is ~/Library/Preferences/com.apple.dock.plist.
If removing that file fails, you'll probably need to start looking deeper into this. You can consult /Applications/Utilities/Console.app. Open this and click "Show Log List" button and navigate to "LOG FILES" -> ~/Library/Logs -> CrashReporter -> and you should see entries prefaced with Dock_ and the date. Open the most recent one for Dock_ and attach its output as a .txt file here.
You'll also want to start asking yourself when it last worked, and what may have changed since then. Particularly any software installations since the time that it last worked and the time it first started acting this way.