It's not the calories bro, it's the alcohol.
Alcohol dehydrates the shit out of ya, acts like a combination of sugar and fat (digests first and takes a long time!)
SO, while it's sitting in your system nothing else is being digested (like your proteins). As far as how long, that depends on the amount and the individual. I know that I don't feel right for a couple days after drinking a couple beers.......
you have a anti-diuretic hormone which controls urination and hydration...alcohol changes the balance of that hormone so you start dehydraging your tissues...
also alcohol is toxic to the liver and should be avoided when doing orals as the combo really whacks the liver cells so they don't function right in protein metabolism...