Getting back to the original topic.
After the update you suggested, everything was OK for a day or two, but now I am losing icons from my task bar again - but, now that I understand what it's doing better I don't think it's a task bar display problem. I think that the task bar is correctly reflecting the fact that the apps are not running.
When they fail to appear on boot-up I suspect it's because there was a problem, possibly with my hard disk. I do have it set to verbose, and I think I can see error messages sometimes, but they fly by so fast that I cannot catch any details. There must be a log somewhere - can you tell me where?