Can't log in to iCloud from Mac after High Sierra update

Hi. I have done High Sierra (10.13.1) update on MacBook and now cannot log into iCloud/iCloud Drive. I enter name and pw, the 'wheel' spins, and then the window for my sign-in details returns to blank, with no error message. I have also lost the files I had on the desktop, though I can see that they are still backed up on icloud (when I go in via icloud.com). I can get into itunes from the MacBook - using same i.d. I also now have problems with Ace Money, which closes spontaneously after a minute or so. All these problems continue if I use Safe Mode. I did a Time Machine backup before downloading High Sierra, so I guess I can return to the previous OS version..... Any bright ideas out there? Thanks