Not sure if this is something to watch for these days (like from a sneaky Win10 update or something that got through), but I just realized the rig with my 980GX wasn't crunching on the GPU. Opened BOINC and the Collatz WUs said, "Missing GPU". Clearly the GPU wasn't missing, but not sure what the deal was. The only way to get it working again was to install the latest NVidia driver. Just sharing in case it happens to anyone else...