Well, USB3 is not supported AFAIK so you need to look in the bios to see if there's a USB2 compatibility option, or whether one of the USB ports on the docking station is USB2 - maybe the other two users plugged their keyboard into a different port?
As a reminder, EEPC6 goes EOL in September this year - https://community.mcafee.com/docs/DOC-5800
The Dell Dock Station E-Port PR03X as 5 Hi-Speed USB - 4 pin USB Type A(2.0). Iv'e plugged them in different USB port with no change.
Iv'e tried 2 other Dell Dock Station E-Port PR03X with the same result.
The Ultrabook E7440 has 3 USB 3.0 port and when he's not docked and the keyboard and mouse are plugged in, it work's fine. The typing at the EEPC screen work's.
Well, if two other users with the same notebook/docking station are working fine as per your original message, it must be a hardware problem with this users device. What's different between them? Maybe BIOS/UEFI version?
One of them as a A07 and the other A08 Bios version.
The one that'S not working properly have a A08 Bios.
Then it would seem that Dell broke something. Maybe there is a newer version you can get from them?
We've found the solution below that works for my case and other one with mouse keyboard problem.
Our McAfee guy adjust this option on the server to "Disable".
Boot Options > Always enable pre-boot USB support is (Disabled or enable?).