I did something similar for a few months (right down to becoming a nocturnal WoW troglodyte). It started when I quit my job to go traveling, and continued after I returned. For me, it was due to a bit of an existential crisis - my 'life script' had always been 'work hard in school, get good grades, get into uni, do well at uni, get a job'. I'd finished the script and was lost. What now, and why should I care?

What dragged me out of this state was the one-two punch of getting a job and meeting a girl. Neither ended up being particularly good for me but they got me started again.