Front USB ports had been working normally. Recently devices such as flash drives, an external hard drive, and a fax modem that are plugged into any of the front USB 2 or 3 ports are not recognized by Windows (7 Pro 64 bit), though the flash drive power lights flash briefly. My USB keyboard, plugged into a rear port, works normally. Device Manager reports all USB devices working properly with the exception of an "Unknown Device" that Windows has disabled.
Other posts have referred to a Via controller; but Device Manager doesn't show any Via device under Universal Serial Bus controllers.
BIOS version is F14.