Hi,
Did you make any changes on the computer prior to the issue?
Method 1:
Try connecting the headphone to other USB ports and check if the same issue occurs.
Method 2:
You may remove and reinstall Lifechat device:
a. Go to Start-> Control Panel (Small or Large icons) -> System icon, and click Device Manager on the left.
b. Expand the Universal Serial Bus controllers
c. See if the first or second entry is "Lifechat Lx-3000 Microphone ".
d. Right-click on Lifechat Lx-3000 Microphone and select Uninstall.
e. Unplug and plug the Lifechat Lx-3000 Microphone onto the computer.
f. In the Device Manager, click the Scan for hardware changes button on the toolbar and let it scan your computer.
When the system finds the new device, it will request to install the right driver.
http://windows.microsoft.com/en-US/windows7/Update-a-driver-for-hardware-that-isnt-working-properly
Also refer the link:
Tips for fixing common sound problems:
http://windows.microsoft.com/en-us/windows7/Tips-for-fixing-common-sound-problems
Enable sound recording for your LifeChat headset