If you face that problem, here’s one solution you should try.

May be when you ‘Add New’ post in your WordPress, you put ‘the expression’ while you writing in ‘Visual’ mode, like this: [vimeo 4012450]

So you have to change your writing mode to ‘HTML’ mode, right beside the ‘Visual’ mode, and put ‘the expression’ there.

Hope this can help you. This make me confused when I use WordPress Video Plugin for the first time. Lucky I try this, and it’s work! (I didn’t read the manual)

Take care!