I can only speak for myself, but perhaps your using a browser that (for some reason unknown to me) dont go well, with uploading pictures to Simply Maya.

I tried to upload with the browser Opera, but I got an error message, stating (aberration itself) that the picture to be uploaded isnt a valid file or something.

Do an upload with the Microsoft Internet Explorer, if everything else fails or produce the same result as above.

Or maybe just upload the picture again.