I have a problem with English listening that has seriously frustrated me.

I'm very good at writing and reading and fluent in speaking. I think I have a high proficiency in English except that my listening doesn't seem to improve. I have been working so hard to try to improve my listening that I think it's near an obsession. I watch English films and listen to BBC radio copiously. I have also watched DVDs with English subtitles. Despite much effort, I still have a great deal of difficulty with listening. What frustrates me is I know nearly all the words that native speakers use (since I have a broad vocabulary), but I just don't seem to catch the 'sounds'.

I'm very frustrated now, and am not even sure if I should continue my quest for better listening skills. Is it possible that my listening has a ceiling, i.e. I can only listen as well as I can now and however much effort I put in, it 's not going to improve further.

What should I do?