IMovie Sound and Audio problem.

I've have IMovie'11 for a while now and everything has been fine up till now. After i have made a project and exited the editing mode and back onto the project select screen, I run my mouse over the project and it goes to a grey screen and i can see my project. I've deleted the cache and that kind of helped. Also when i import a movie i can't hear any of the sound? It's really odd and i hope it's nothing too serious.

Please help.

Thanks.