Tvheadend

I am struggling to get a TeVii S660 card to work reliably with TVHeadend. I am running Ubuntu 12.04.1 LTS (GNU/Linux 3.2.0-36-generic x86_64) with TVHeadend 3.2.34.

The card tunes and finds muxes OK with the latest firmware from TeVii, and I have also tried alternate firmware identified in this thread:

http://ubuntuforums.org/showthread.php?t=1378994&page=16

I have enabled proprietary DVB drivers with jockey-text. I am able to watch channels on this card in XBMC but find that having tuned to this card, XBMC then loses the TVHeadend connection with the following messages repeated at 10 second intervals:

13:16:07 T:5712 ERROR: AddOnLog: Tvheadend HTSP Client: connection dropped, trying to restore
13:16:07 T:5712 ERROR: AddOnLog: Tvheadend HTSP Client: CHTSPConnection::ReadMessage - not connected
13:16:07 T:5852 NOTICE: AddOnLog: Tvheadend HTSP Client: CHTSPConnection - CHTSPConnection::SendGreeting - connection opened to 'HTS Tvheadend 3.2.34~gfaee94b~precise', protocol v6

In TVHeadend, I am also seeing the following repeating messages:

Jan 19 14:00:48 dvb: "ASTRA: 11,223,670 kHz Vertical (Default (Port 0, " on adapter "Montage Technology DS3000/TS2020", status changed to OK
Jan 19 14:00:49 dvb: "ASTRA: 11,223,670 kHz Vertical (Default (Port 0, " on adapter "Montage Technology DS3000/TS2020", status changed to No signal
Jan 19 14:00:56 dvb: "ASTRA: 11,223,670 kHz Vertical (Default (Port 0, " on adapter "Montage Technology DS3000/TS2020", status changed to OK
Jan 19 14:00:57 dvb: "ASTRA: 11,223,670 kHz Vertical (Default (Port 0, " on adapter "Montage Technology DS3000/TS2020", status changed to No signal
Jan 19 14:01:04 dvb: "ASTRA: 11,223,670 kHz Vertical (Default (Port 0, " on adapter "Montage Technology DS3000/TS2020", status changed to OK
Jan 19 14:01:05 dvb: "ASTRA: 11,223,670 kHz Vertical (Default (Port 0, " on adapter "Montage Technology DS3000/TS2020", status changed to No signal

I need to restart the TVHeadend system to be able to connect from XBMC.

I have no issues when just using the other tuners connected to TVHeadend (PCTV nanoStick T2 290e and Hauppauge WinTV Duet).

The card seems to work OK when attached to Windows 7 Media Centre.

Any help with identifying known working firmware, configurations, etc. would be much appreciated. As would suggestions on where to look to better identify what the problem is.