Which clock are you talking about? The one in the post immediately above this (http://www.homelandsecurityus.net/CountDown.htm) is not encrypted. It looks like very normal JavaScript code - nothing that could possibly cause problems on someone's computer or browser.
The Bush countdown clock uses a server-side CGI script or similar - in general such a script will never be visible in the browser, just its result. There's nothing "encrypted" here either.
But there are any number of countdown clocks and knock-offs of each other around the net, if you're talking about another similar clock then all bets are off. There may well be a countdown clock out there that contains a virus ... however virtually all browsers nowadays prompt you before trying to run an unverified executable. (JavaScript doesn't count because it's not in the programmer's vocabulary to affect things on your computer outside of your browser and your cookie file).