If your MacBook shuts down without warning, a new Web site says that you may not be alone. The site, macbookrandomshutdown.com, is <A HREF="http://www.eweek.com/article2/0,1895,2010330,00.asp?kc=EWNAVEMNL083106EOAD">dedicated to the random shutdown problems</A> encountered by the owner of a 2GHz MacBook purchased in the summer of 2006. About four weeks after it arrived, the MacBook began randomly shutting down without explanation. So, Matthew Swanson of Atlanta, Ga., decided to take his concerns and turn them into Web site and message board for people to post blogs and comments about similar MacBook problems.