I've experienced strange bug with updating from stable to beta version. I use MultiUpdate for update and after update completed MC doesn't start with error message which complain for broken configuration. I copied MC from C: drive to D: drive and update installed without any problem, afterwards MC start as usual. Very interesting moment: MC updated to beta flawless on other PC and on my USB stick. All my MC copies is portable versions.
All my PC runs Windows 8.1.
I have not seen anything like that.
There was probably more information about what exactly was wrong in the logs, if you reinstalled they are now gone.
Sorry for false alarm. Seems this is some troubles with directory rights.