Won't Boot, Download Mode Can't Connect to PC (USB errors)

I recently updated my S4 mini LTE to 5 (Lollipop), after restarting shortly thereafter the stock and unrooted phone was in a boot loop, recovery mode showed error “failed to mount /data - (invalid argument)”. Tried to connect to USB to reflash ROM, but phone is not recognized (see errors below) using Linux and Windows on four PCs attempted (one desktop, four different USB cables). USB port was cleaned and solder/connections seem intact. Suggestions?

Errors:

usb 6-2: new full-speed USB device number 3 using ohci-pci

usb 6-2: device descriptor read/64, error -62

usb 6-2: device descriptor read/64, error -62

usb 6-2: new full-speed USB device number 4 using ohci-pci

usb 6-2: device descriptor read/64, error -62

usb 6-2: device descriptor read/64, error -62

usb usb6-port2: attempt power cycle