Sorry if this has been mentioned in WB beta thread.

Symptom is what title says. After first start (and restarts if desktop isn't made visible) only mouse cursor is visible. ctrl-shift -esc shows task manager from which I can close WB tasks and run new explorer task after which the desktop appears. Restart after that and everything works again.

If I just run explorer from the task manager without killing wb first nothing happens. Next restart I get black screen i.e., identical symptoms. If I kill wb, run explorer everything works well from that on.

Unfortunately I can't be sure if it's WB or wfx that is causing this as I killed both processes. Although when I did not have WB installed updating insider preview worked just fine.