So, after I only rebooted my computer next morning, it seems everything works fine, after all no crashes anymore, however, I don`t know why.
But I have another problem still exist since I updated to NB 6.3b, and a new one too. First the older one:
NB is loading partial files (xxx.nb2) in the download directory now (before I preferred the option to load partials into a separate sub-folder) but since 6.3b now sometimes NB seems to forget to complete files and didn`t write them as "original" files (for example: xxx.rar) and delete the partial files (xxx.nb2). But on my download list NB shows this files as completely downloaded and put the "downloaded" icon in front of it. In some cases NB wrote the RAR file after some minutes or hours on the disk and deleted the old nb2 file. But in other cases not, I still have a few nb2 files there from days ago.
Second problem:
Since my update to 6.3b, NB have problems to connect to my news server ([16:22:15] ERROR NNTPSocket - NNTP Perform Auth - news.tweaknews.nl-The server rejected your login - contact your news service's support department. It's not a Problem with Newsbin : 400 news.tweaknews.nl: Your per-user connection limit reached -
info@tweaknews.nl). NB now sometimes need up to 5min until it get a connection
Sure it`s looks like a server problem, but I never ever had problems like this before with my news server.