Ya, it happens to me pretty regularly. Every night that I'm browsing the forums at 11pm EST. (Pretty usual time for me, right before I go to bed).
From about 11PM EST to 11:15-11:20PM EST any zam.com or allakhazam.com page is unavailable. Usually a 503 or an [error occurred while processing this directive]. Sometimes it's only 5 minutes or so but like today it took until almost 11:20PM EST for the site to become available again.
I remember there being a thread about this before. I think which ever admin responded took some notes and ended up splitting up the server maintenance stuff to alleviate the server load at the specific times.