I had to spend last wednesday evening doing a kind of system restore.
OneDrive had finally gone completely bananas, and insisted on stating there was no internet connection, meanwhile sync still worked properly, except the indexing engine consumed all disk capacity on the boot drive, and huge loads of CPU as well.
First I tried a system restore, since I also had a problem with DirectX or the NVidia graphics drivers, where especially CoD:AW continually crashed a few times every day.
That didn’t help at all and actually made things worse since Dropbox stopped working after the restore. Which led to an rollback of the system restore and brought me back to where I was, with the same OneDrive problems unfortunately.
Next attempt was simply to delete my user profile, which felt somewhat risky since it had grown to 175 GB, but all data was supposed to be safe in the cloud so… to boldly go…!
Profile deleted, account needed to be deleted as well, and then re-created, then I could login without errors, and lo! OneDrive started working properly!
And surprisingly much else just started working right out of the box. Steam did not even glitch, some icons for Password Safe and Dropbox went missing but all data was there, even favorites in Firefox since I’m using XMarks. So far the only thing I really have found not working was the start page, plugins and settings in Firefox, and since these could be quite a pain to restore I took a shortcut and exported the whole Firefoxprofile from another computer and loaded, which worked nicely.
It took a few hours for OneDrive to fully resync itself, but apart from the waiting time all now seems fine so I guess it was worth it. If only I could now find the cause or solution for the DirectX error as well.