Try deleting the "com.apple.Dock.plist" file in /Users/Yourname/Library/Preferences and then open Terminal. Type the following in terminal:
killall Dock
Press [ENTER]
You might need to re-add any icons you added to the dock as it will go back to the defaults. Since the dock goes back to the default, Dashboard should also work as normal.
Hope this helps. 🙂