I know that you need to eat protein to get the benefits of lifting weights, however, I wonder, is it better to have said protein enriched meal before or after the actual workout? I usally do it before but there are occasions when my schedule doesn’t permit and I have to settle for working out a couple hours after dinner (one of the advantages of weight lifting is the fact that darkness and weather tends to be less a factor in workout time, unlike going for a run, which I perfer to do before night falls).
To get the full benefit of training, aerobic or anaerobic, it’s best to have a small meal containing both protein and carbohydrate after your workout. I can’t remeber where I first read it… possibly in this book http://www.amazon.co.uk/exec/obidos/ASIN/0719031648/qid=1041433789/sr=1-1/ref=sr_1_0_1/026-2082374-1206019 but this confirms it http://menshealth.i-a.co.uk/ask/view.php?id=46
Carbs are important in a post workout meal- Your body has stores of glycogen to replentish. Both in the liver and the muscles.
The protien is just important to start the muscle building process. Not sure if there is any other reason. 
Actually, the protein in your post-workout meal makes your body absorb the carbs faster. I got that little tidbit from a book by Edmund Burke titled “Optimal Muscle Recovery”. Definitely worth looking into–the research seems to be pretty solid, and the program he outlines seems to work.
I seem to recall reading somewhere that it’s good to have some protein before a workout, so that protein synthesis can begin as soon as possible, but I don’t have my source handy.