This is becoming all rather tedious now! So the fix lasted for one day until yet another wpforo update (1.9.3)
So after 1.9.2 the widget worked correctly which is why I thanked you above. Then you release 1.9.3 in response to some other bug and the widget reverts back to not working again!!!! (see attached below)
As I say this is all very tedious. Congrats though, now it hides any sensitive text on the widget from the private forum thread and leaves it all blank. Oh and they all say 51 years ago as before.....
Guess I'll just have to go back to disabling it again!
Working as expected on 1.9.3 on my boards.
Also, go to Dashboard > Forums > Dashboard and click the [Clean Up] button to remove orphan / damaged topics and posts.
Firstly, apologies for the tone of my first post, reading back it comes across badly, no excuse just frustration blinded common sense and manners.
Secondly, I tried all the cache options suggested and it failed to rectify the reported problem, however here are some observations.
After a few minutes pass and I navigated around a few posts, those private "empty" posts of "51 years" ago vanish from the recent post widget list. All good you and I might think. However, they appeared back later on, then disappear once again. This is most odd and I've no idea what is going on to cause such behaviour.
If you go to the forum now they're gone but you can bet they'll pop up again later.
Thought I would just say 30mins after posting the above, the phantom private forum widget entries are back