I've upgraded to 6.51 from 6.42 and noticed that when a download completes the chunks are not always being deleted from this new common folder in the data folder.
At the moment I've got 105 MB of chunks left over from 8 downloads I've done today, it might not sound a lot but it will soon add up after a while.
Why aren't they being automatically deleted and can they be manually deleted?
I also seem to be having a problem with header downloads in some groups, in that I've deleted the stored posts, downloaded latest with download age set at 2 but nothing is showing up in the group list even though headers have been downloaded.