On my way to compile a compiler I must have messed my NAS up. The ipkg install command aborted with ipkg_download: error: command failed with return value 139: 'wget --passive-ftp - q - P ...'. therefore my first step was to reinstall the bootstrap. Since this needs rebooting after deleting the @optware directory, I detected that port 5000 was not reachable. I first figured it to be some issue with port forwarding of the router. Then I checked the running processes on my NAS. Right you are no httpd process was running that would back the web UI. Therefore the port 5000 and 5001 were not open. Trying to restart with /usr/syno/etc/rc.d/S97apache-sys.sh start issued also a Segmentation fault. Therefore it suggests itself that some way along my trails some piece of binary code was introduced that resulted in this.
The resolution was that I reset the station, installed the firmware, the bootstrap and subversion again.