I don't know if this can help but,... As you may know my mother language is Spanish. I studied English at school and at the university.
I learnt a lot of grammar, but my "problem" is -also- understanding. Of course it is easier to read and understand what you are reading, as you have all the time to do it. When listening, as Angie mentions, (�Hola, Angie!), if you haven't got much practice, you have to "process" all that information.
But, that's a question of practice. Listen to Spanish songs, videos, films, etc... and your listening abilities will improve.
When I was 15, I used to listen to looots of songs in English, and, without reading the lyrics, tried to understand the words. When I was not able to understand I concrete word, went to the dictionary. Sometimes this didn't work, sometimes it did, and, with the practice, all those songs started to have a meaning!
Hope this helps!