Look at the BIOS parameters before boot, there should be an option to enable/disable the Usb EHCI (enhanced host control interface). As far as I understand it is enabled by default, but a previous user may have disabled it.
You can obtain basic diagnostic information from the Windows event log, and since you have access to an oscilloscope you might want to try a tool for Usb electrical analysis (see http://www.usb.org/developers/tools/
This is a laptop, I have very limited options. There is no EHCI option in BIOS.
One thing to consider is what version USB ports do you have? I've had problems using my Leonardo on USB3.0 ports. I had to move it to a USB2.0 port to work correctly.
This is an old computer, HP zd7160us. P4 running Win XP SP2 and Java 7. The USB should be 2.0.
Thanks for any continuing help. I may just have to run on another computer if I can't figure it out, but I don't see any reason why it shouldn't communicate.