David Baron pointed out at the "War on Orange" meeting today, you can get Tinderbox logs much faster if you avoid using the "showlog.cgi" program.
For example, if you have a build log URL:
http://tinderbox.mozilla.org/showlog.cgi?log=Firefox/1284748812.1284749884.15885.gz
You can remove "showlog.cgi?log=" from the URL, and you'll download the log directly, i.e.:
http://tinderbox.mozilla.org/Firefox/1284748812.1284749884.15885.gz
This will download much faster, and you can grep for the text you're interested in directly in the downloaded log.