Guys and developers,
I found the problem. The Ctorrent included in the WD ShareSpace supports only http trackers and not udp ones. Whenever a torrent file has also udp trackers in it, Ctorrent gets stuck in 'connecting to tracker' status. Easy way out from this problem is to edit the torrent files (e.g. torrenteditor.com) and remove the udp trackers. Done that, Ctorrent will work fine again.
It would be of course great as long term solution, if the developers could enable the support to udp trackers in the embedded Ctorrent. Based on my reasearch Ctorrent as such should support also udp trackers.
The above has been found and fixed as described also with the latest firmware 2.3.01.