Sparse bundle on NAS - can't open "Resource temporarily unavailable"

I just got a new Lacie NAS with their NAS OS 4. After making an initial Time Machine backup to this device I wanted to mount the resulting (encrypted) disk image but when doing so I just received an error message "Resource temporarily unavailable". Googling this error message returned a lot of Voodoo fixes. However, after playing around a bit, restarting a few times etc I realised that I had something called Time Machine service enabled for this share. Turning this service off immediately made the disk image available as expected.