This issue has been fixed by Microsoft. We suggest updating to the newest version of Windows 8.1 via the Windows Update tool. If for some reason you are unable to download this update, this fix should still work, but we highly recommend updating to ensure you have the latest Windows security fixes.

Users running the newest Windows 8.1 have reported an issue where their DataLocker DL3 will disconnect after a certain period of time, even when changing the USB Selective Suspend Settings to off. This is a problem caused by Microsoft's handling of power profiles and we have reported the issue to Microsoft and are waiting on a patch. Right now, the problem can be fixed. However, this involves changes to your registry, which if done incorrectly can require a reinstall of Windows! Only do this if you are confident modifying your registry, as DataLocker offers no warranty if this advice damages your PC! 

You will need the Vendor ID and Product ID for this fix, which are as follows:

Hardware ID Info: VID_230A&PID_1180

This website has the walkthrough for fixing this issue.