Hi Bernie

Glad it’s now working.

It sounds like it was a classic case of the USB port being overloaded and the safety trip cutting in, with the normal way to reset it being to power the computer down and unplug it.

Although the USB socket specification specifies the power output of USB controllers, some manufacture cut it down to the bone or fit over sensitive trips. (Hence you found it to be a common problem with certain Dells)

Regards

Bill