The Glitch  That Stole Holiday Buys Online shoppers intent on skipping long lines and clogged parking lots at the mall are discovering a different kind of traffic problem this holiday season: overcrowded Web sites that are cracking under the pressure.  &lt;FONT face="verdana,MS Sans Serif,arial,helvetica" size="-2" color="#666666"&gt;&lt;B&gt;-The Washington Post&lt;/b&gt;&lt;/font&gt;