I switched to digital cable recently, which means that there is now an external cable box for tuning. That means the analog tuner on my mythbox must be set to channel 3 to receive the input from the cable box. Unfortunately, ivtv-tune has a quirk that made it difficult to get the PVR-250 tuned to channel 3. The problem is that ivtv-tune needs the HOME environment variable to be set, and it needs there to be a ~/.ivtv-tune file there. Finally I got it working with this upstart script:

# Ensures the PVR 250 card is set to channel 3 so that the cable box works.

description "Ensures the PVR 250 card is set to channel 3"
author "Matt Hughes "

start on mounted
stop on starting shutdown 

task

console output

script
echo "Changing tuner to channel 3..."
export HOME=/tmp
echo "device /dev/video0" > /tmp/.ivtv-tune
echo "freqtable us-cable" >> /tmp/.ivtv-tune
exec /usr/bin/ivtv-tune -c 3 -d /dev/video0
end script

Now the ir-blaster can do it's thing and everything works. As a side note, if your remove control stops working, you should replace the batteries be for messing with the LIRC configuration, even if you just updated your kernel. !$!@#$@# Linux.