We've seen this when security software blocks the users ability to write to CD/DVD's. Run gpedit.mscand go to Windows settings>security setting>local policies>security options and make sure Devices: Restrict CD-ROM access to locally logged-on user only is set to disabled.
Also, too many entries for mounted devices in older computers can cause this problem. When all the entries cleared the drive should work again. To do this, go to start and type regedit in the search field. Make sure to back up your registry before making any changes. Here are instructions for backing up your registry.
http://windows.microsoft.com/en-US/windows-vista/Back-up-the-registry
In the directory list on the left side, find the entry HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices. Remove all entries except for default (it won't let you anyway).
You can also look at Device Manager when the Data Traveler is connected to see if the drive comes up with any yellow exclamation marks. Uninstalling the device with the exclamation mark and scanning for new hardware sometimes will work as well. You may want to try this even if you do not see any yellow exclamation marks for this device. You will need to run the uninstall as the Admin to be able to perform this while logged-in as a non-Admin.
Also check the setting for your security programs (Norton, Symantec, etc).
FAQ: KDT-121311-PRV-03