[mythtv-users] Problem controlling external tuners in new upgrade using mythtv V0.25.3

[Craig Huff]

I am using the contributed program "channel" for changing stations on
a Motorola DCT-2xxx settop box supplied by Comcast using the serial
port connection.

I am also using the contributed program "change-channel-lirc.pl" for
changing stations on Comcast DTAs using hardwired optocoupler isolated
connections to the DTAs' sensor extension ports.

These have worked unfailingly under Mythbuntu 10.04 (mythtv V0.23).

These are working without problems under my default user login from
the command line as well as under the mythtv login from the command
line.

Neither is working correctly when using mythtv to change stations,
either in live TV or for recordings.  When I test channel changes in
live TV mode, I get errors about missing video output and the system
is locked up for some time (10 seconds? 20 seconds?) before getting
unceremoniously dumped back to the frontend menu.  If I open up a
terminal session while live TV is running and change the channel that
way, the channel change occurs with no muss or fuss, no matter what
user name I am logged in as.  I am even using the exact same command
strings defined in the backend settings, which are fully specified
pathnames to the channel changing programs.

Under Mythbuntu 10.04 / mythtv V0.23, the tuning programs progress
messages were logged in the mythbackend.log, but I don't see them (or
anything else relating to the tuning problems) in mythbackend.log
under Mythbuntu 12.04 / mythtv V0.25.3.

Can anyone help figure out what is going amiss?

TIA,
Craig.