Good news - RC2 seems to work fine!
I was using RC3 (64-bit) for some time until it disappeared suddenly. After restarting - keeps closing every time - a windows dialog keeps appearing informing that Newsbin is stopping.
I then started RC2 which worked just fine.
After a while I switched back to RC3 - working fine too. So far.
I suppose, some specific download was causing the problem, I should have caught which one.
But still, better look out for similar issues.
Also, I noticed that the free space on the drive with NBData is being gradually consumed even when no new headers are downloaded.
It seems that Chunks folder keeps growing and growing. Even when the stuff is downloaded and no longer in the download list, (some of?) related chunks remain not deleted.
In less than a day I got 16 GB of such orphan chunks that I deleted manually because the related downloads were already completed successfully.
The stopping of Newsbin was not caused by deleting of those chunks - I deleted them later, after the forced episode with RC2, but I noticed those growing chunks earlier, before the episode with RC2.
All that garbage was created with RC3 and not before - it was clear from the dates of the files.
So two issues.
Both issues occurred with AutoPar disabled. I was using RC3 with AutoPar enabled too, no problems detected.
But those issues perhaps might be related to particular posts rather than to the enabling/disabling of AutoPar - not for me to judge.
Sorry for not providing more specific data, like specific posts. I should have thought about it earlier...
UPDATE:
stopped working again - this time with AutoPar enabled. I think I had enough. Going back to RC2 until RC4.