Dell Latitude E6430 Keyboard stops responding

I have several Dell Latitude E6430 PCs that I use external wired USB keyboards with. After a while (~ one hour?) the keyboard stops responding. If I wait long enough (15 minutes?) I can start typing again. It seems that the notebook keyboard also stops responding. I am using external monitors via e-port replicators. There have been times when I am able to type ONLY in a certain field. For example a form in an IE window that is running in compatibility mode. I do not have an issue within VMware Workstation 11.

I have restored to factory image, reloaded software and still have the problem. I have updated BIOS and drivers. I have removed USB controllers using Device Manager and restarted. Still have issues.

Systems are using Windows 7 Pro.

Curious if other software might be causing issues. Some installed programs include MS Office 2013, Notepad++, Paint.net, BeyondCompare, VMware Workstation 11, FileZilla, Greenshot, Google Drive, Chrome, Tracker PDF Viewer, GoToMeeting, Kaspersky Internet Security.....