I found another answer to this on under wont change channels when recording.
Mine was doing same as yours.
I did as suggested thats was turn off, remove ariel, turn on and go to installation and default- this deletes all but the progs on disk (i.e. all channels and any schedules for recording).
Then starts retune, turn off on remote then at plug, put ariel back in and on again and tune in.
Also I think that if you have a lot of recorded programs on disk (more than 50) this seems to slow the thing down, so I also deleted a lot of stuff.
Jason, July 2009