I think I've found my problem.
I ran top in a terminal and found a process running at 99%+ all the time.
AGAdminService.
This service is the Citrix Access Gateway service. I use Citrix to log in to work remotely. For the time being, I think I will need to scrap it.
ETA:
https://discussions.apple.com/thread...art=0&tstart=0
H