Well, I used Revo Uninstaller to remove all traces of Trimble Update SU version, and re-installed previous SU version, and.....same problem.
I have finally traced the problem to a faulty, intermittent usb connection on my external hard drive. That drive contains all the files I work on regularly (including all my SU files) and I connect it to either my desktop or laptop. I work from that drive on whichever computer it's connected to, and save anything I've changed to it, backing it up whenever it's connected to my desktop. The day before the skb problem started I had just installed the drive in a new external enclosure, and the usb connector did not fit correctly to my motherboard connection. Whenever it would briefly disconnect is when the problems would arise.
Anyhow, I have fixed that problem and everything is working fine now.
Even tho the Trimble update was not the bad guy, I'm not going to update any of my computers. I've had a long-standing policy of not updating anything right after the update becomes available, instead waiting until I feel any bugs have been discovered and fixed. This has kept me out of trouble a number of times. I'll wait until a significant update comes out (after I feel it's safe)
Thanks again to everybody.