ReadyNAS NV+ suddenly gives error -36 connecting with CFIS

While trying to solve a problem with my TimeMachine, I did a few things that - while solving my TM issues - also killed my CFIS access.

The issue with TimeMachine was that I had turned off the TM temporarily, and when I turned it on again it prompted me to change the disk allocation to a lower size. The TM stopped working altogether, giving a disk error. It seems likely that this new size was under the old sparsebundle size, and this might be causing the error. I rebooted with volume scan and quota fix (don't know exactly what that should do but it sounded sensible to start), but this did nothing.

Reading up a bit, I decided to turn off TM altogether and delete the sparsebundle via Finder/CFIS and start afresh. I turned off TM in Sysprefs, turned it off in ReadyNAS, and while I was doing that updated to v4.1.18. I used Finder to delete and, while deleting, Finder hung up on me, and quit unexpectedly. Ever since, I have not been able to connect via CFIS.

I decided to try my first (*gasp!*) SSH attempt ever. First I used 'Enable Root SSH', and then later 'ToggleSSH' to turn it on/off. SSH'ing provided access to the .timemachine dir again, and lo and behold, the sparsebundle was still there. I deleted the sparsebundle in full (have not yet attempted new backup, hope it will work). Have rebooted and done volume scan and quota fix. However, CFIS is still down. When trying to connect with Finder it gives Error Code -36, seemingly an I/O issue. SSH still works fine.

How do I get CFIS working again?