Hi,
Copying over the reply I posted there...
UpdraftPlus was tested against WP 4.2 beta 3, and the current release of UD works with that. More changes to how updates work were introduced in WP 4.2 after that, and we’ve been active here and in Trac co-operating with the core team over those. We have a release that makes everything happy again on rc1 that completed testing at the end of last week should be released to the world later today.
That release was made earlier today - so please let us know if you still have problems.
Best wishes,
David