After updating to Beta 3 just now, my settings were reset (as usual), and after setting the resolution and a few other options I was asked (as expected) to restart.

After restarting however, my mouse cursor has disappeared.

I have started tweaking the prefs.ini by hand to try and see if I can get it back, but have yet to determine what triggers the problem.

Update:

even removing prefs.ini and/or setting hardware cursor have no effect...

Update 2:

after rebooting everything is back to normal...