Since the release of 10.5, I've seen that the execution of AppleScripts triggers heavy activity of syslogd, basically causing it to take over the CPU. I've found that by killing the syslogd process (which will automatically restart) and removing the asl.db file from the /var/log directory, I can at least temporarily solve the problem.
Here's a two-line AppleScript to do just that:
Mac OS X Hints
http://hints.macworld.com/article.php?story=20080702175757558