Why won't my macbook show the dashboard or fullscreen windows?
I think you have too many junk files
here is what to do:
1.Delete Files you no longer need.
2.Empty Trash. Having too much junk slows down your laptop
3.Install A program that cleans your laptop

Or maybe there is a virus installed in your computer
here is what you have to do:
1.Move the file you think may be causing the bug.
2.Install MacKeeper
3.Run MacKeeper and scan your pc for viruses
4.If the app found a virus delete it

so thats it thanks!