Code 38 Error. Window Driver UDBSTOR.sys

My Win 8 x64 desktop suddenly stopped recognizing USB storage devices (Thumb Drives & 2 External HDD). When working through Device manager, all show yellow exclamation marks and working through properties, all say "Windows cannot load the device driver for this hardware because a previous instance of the device driver is still in memory. (Code 38)". The driver in question is USBSTOR.exe. I think this is a generic windows Driver, so Win 8 is likely broken in this regard. I've rebooted many times, removed the devices using the control panel and swapped USB ports with no fix. The driver rollback option is not available & Control Panel says the driver is up to date. Not sure where to turn. Would like to avoid Reset and Refresh due to the time demands of setting up programs again. May try System Restore if no direct fix works. Thanks MBO - ASRock Z77 Extreme 4

Sorry that I had a typo in the title. The driver is

USBSTOR.sys