Tvheadend

Hi, wonder if anyone can help with recording with the following set up.

Raspberry Pi running raspBMC
TV headend back end working, can configure using web interface, have found tuner, channels
TV headend front end on XBMC working, can watch live TV (MPEG2 licence present)

I want to record to a smb share on a Windows Home Server 2011. RPi can access this server for other media no problem.
Using TV headend web interface I set recording location to /media/recordedtv and mounted a folder on WHS to this location in fstab. I can browse from the command line to this location and can play videos in this folder via the mountpoint from XBMC (i.e. credentials are working).

Any attempt to record gives error message "couldn't save timer"

Thanks all in advance for any advice