I recently switched from a ASUS ZenBook Touch to a Lenovo X1 Carbon. All was well until a few days ago when I let the battery completely drain while watching a movie. Since then the X1 Carbon was sluggish while plugged into my Targus ACP71USZ Docking Station. It wasn’t sluggish with just power or just external monitor, but the combination of those two things made the machine unusable. I’m not 100% sure letting the battery drain caused the issue, but it was the only thing I could think of that would impact the system. I didn’t install any software or do any Windows Updates during that time.
I pinged my contact at Targus and he recommended I update the BIOS that enables USB 3.0 on the X1 Carbon. I found the BIOS Update Utility for Windows 8.1 at Lenovo.com, ran it, rebooted and all is well now. I have power and two external monitors running through the Targus ACP71USZ without any issues.