Screen lock not getting off

You can reset it using iTunes. Open iTunes, plug the iPod in using USB, then turn of the iPod, once it's off hold down the home and lock buttons for 10 seconds, then release the lock button while continuing to hold the home button. After a few seconds iTunes should detect the iPod and you can reset it to factory defaults.

You can reset it using iTunes. Open iTunes, plug the iPod in using USB, then turn of the iPod, once it's off hold down the home and lock buttons for 10 seconds, then release the lock button while continuing to hold the home button. After a few seconds iTunes should detect the iPod and let you restore it without the code.

What generation? What do you mean, the slide to unlock, or the screen lock? If you mean the screen lock, you should connect to iTunes, because some iPods unlock after connecting to iTunes. Otherwise you should reset it with iTunes. But then all your data will be lost. Otherwise you should try try try. You've got 10000 chances ;-) If you have an iPod Touch, you might mean the slide to unlock screen is frozen. I had that one time, after trying out spoken feedback. After that it locked the screen and the touch screen wouldn't work anymore. I couldn't do anything anymore, not unlocking, not turning off spoken feedback, not even turn off the iPod. I was lucky to find there was an update for the iPod so iTunes turned it off. Then it responded also again.
More details next time please!

If it was locked and you donot know the password then the only thing you can do is restore it using dfu mode hold both power and home button until it turns off and restart and show you to connect to iTunes. Then restore it. Let me know what happened.

Screen Lock only locks users out of the user interface. It does not encrypt data on your iPod.
For example, if you use Screen Lock and then connect your iPod to a computer, you'll still be able
to manage music on your iPod with iTunes and access all data on it in disk mode (contacts,
notes, and any other files you have stored on the iPod).

To unlock it, connect iPod to the primary computer you use it with (the first one iPod synced with),
and open iTunes. When you disconnect iPod from the computer, it will no longer be locked.

If you can't unlock iPod using this method, you can restore your iPod to factory settings. Please
note that this will erase all data on your iPod. Afterwards, you can add your music and data back to iPod.

To restore your I-pod, do this:
1) Ensure that you have an active Internet connection as new versions of iTunes and iPod Software
may need to be downloaded to your computer.
2) Open iTunes, and then connect your iPod to your computer using the USB or FireWire cable that
came with your iPod. After a few moments, your iPod will appear in the Source panel in iTunes.
3) Select your iPod in the Source panel and you will see information about your iPod appear in the
Summary tab of the main iTunes windows.
4) Click the Restore button. You will be prompted with one or more restore options that may prompt
iTunes to automatically download the latest iPod Software. Use restore option 4.

In the Apple Support Site, Apple notes that the "Screen Lock" function:
Allows you to set a 4-digit combination to prevent someone else from using your iPod while it is not attached to a computer. When an iPod is locked, you must enter the combination to unlock the screen. This feature is different from the Hold switch in that the Hold switch only prevents iPod from turning on accidentally -- not keeping snoops out. Screen Lock only locks users out of the user interface. It does not encrypt data on your iPod. For example, if you use Screen Lock and then connect your iPod to a computer, you'll be able to manage music on your iPod with iTunes and access all data on it in disk mode (contacts, notes, and any other files you have stored on the iPod). This supportdocument aso provides additional information on locking and unlocking the iPod. According to Apple, if you have forgotten the code, you can unlock the iPod by doing the following:
Connect your iPod to the primary computer you use it with (the first one iPod synced with), and open iTunes. When you disconnect iPod from the computer, it will no longer be locked. If you can't unlock iPod using either [the code or connecting it to the computer you use to manage its songs]. . . you can restore your iPod to factory settings using iPod Updater. Please note that this will erase all data on your iPod. Afterwards, you can add your music and data back to your iPod. If you want to change the primary computer that your iPod is associated with, do this: 1. Restore your iPod. Warning: The restore process cannot be undone. All of your songs and files will be deleted. Always make a backup of your important data. 2. Connect your iPod to the computer that you want to be the primary computer. 3. Open iTunes and synchronize.

"Screen Lock" is provided by the iPod nano, iPod (5G), and subsequently released iPod models. Earlier iPods do not offer this feature.
In the Apple Support Site, Apple notes that the "Screen Lock" function:
Allows you to set a 4-digit combination to prevent someone else from using your iPod while it is not attached to a computer. When an iPod is locked, you must enter the combination to unlock the screen. This feature is different from the Hold switch in that the Hold switch only prevents iPod from turning on accidentally--not keeping snoops out. Screen Lock only locks users out of the user interface. It does not encrypt data on your iPod. For example, if you use Screen Lock and then connect your iPod to a computer, you'll be able to manage music on your iPod with iTunes and access all data on it in disk mode (contacts, notes, and any other files you have stored on the iPod). This support document also provides additional information on locking and unlocking the iPod. According to Apple, if you have forgotten the code, you can unlock the iPod by doing the following:
Connect your iPod to the primary computer you use it with (the first one iPod synced with), and open iTunes. When you disconnect iPod from the computer, it will no longer be locked. If you can't unlock iPod using either [the code or connecting it to the computer you use to manage its songs]. . . you can restore your iPod to factory settings using iPod Updater. Please note that this will erase all data on your iPod. Afterwards, you can add your music and data back to your iPod. If you want to change the primary computer that your iPod is associated with, do this: 1. Restore your iPod. Warning: The restore process cannot be undone. All of your songs and files will be deleted. Always make a backup of your important data. 2. Connect your iPod to the computer that you want to be the primary computer. 3. Open iTunes and synchronize. Apple also notes that company "representatives cannot unlock an iPod if you forget your combination. If you can't unlock your iPod and you don't have access to the primary computer, your only option is to restore the iPod, which will erase all music and data."