It appears that, literally overnight, DynDNS decided to cancel my free-tier account which I've had since 2000. Apparently, they changed their SLA 30 days ago, requiring that all free-tier account holders must login to their admin panel once per month or face cancellation of services. Unfortunately, the email address I had on file with Dyn is a Yahoo! account I rarely check.. bummer.
So what does this mean? Well, it means that your update.bat file is pointed to jdolan.dyndns.org which no longer resolves. We're working on a new snapshot to fix the issue for new users, but if you already have the game installed and want to fix it, open up update.bat and change:
... rsync://jdolan.dyndns.org/...
To:
... rsync://quake2world.net/...
Apologies for the inconvenience.
New snapshots on the website contain a fixed update script. Folks should be good to go now..