i had the same problem with my wii-remote. i do it this way: map "F6" in mythtv to delete a recording. the problem is, you have to click "F6" twice. With the first click it shows the mythtv-delete-window and the lmce menu to change channel. With the second click on "F6" the lmce-menu disappears, but the mythtv-delete-recording window still stays there and you can delete the recording.