EDIT: As Chris pointed out, as long as the buttons are still functional, you can force a restart by holding down the home and lock buttons for ten seconds.

Just about five minutes ago my iPod Touch’s (Second Generation Model MB528LL) screen stopped responding to my finger. The screen itself still worked as did the the physical buttons. The dang thing just wouldn’t respond to my touches. So, assuming it’s not some sort of hardware malfunction, you need to restart the device. There are two ways to do this. For a force restart you can hold the lock button and home button at the same time until you see the device restart. The second way may be a little safer but more complex. Yes, SSH. You need to:

1. Find or guess the IP Address or Hostname of your iPod. Sometimes your router’s web interface will tell you.
2. On Windows, download PuTTY. On Linux or a Mac open up the terminal.
3. In PuTTY, type in the hostname or IP you found. Then hit open. On Linux/Mac type “ssh root@(hostname/ip)”.
4. When you’re asked for a username in PuTTY put in root. When you’re asked for a password, put in the one that you changed it to. If you didn’t change your password try “alpine”.
5. Now you should be logged in to the device as root. To restart the device type “reboot” then hit the enter key.
6. Your connection will be closed and your iPod or iPhone will restart. Hopefully, when it boots back up it’ll now be fully functional.

If this doesn’t restore touch functionality to your iPod then it very will could be some sort of hardware defect. I’d give Apple Tech Support a call and pray it’s under warranty.