Overdubbing Midi

Hi All

I have been recording and overdubbing midi for years without any issues, and now suddenly, I can't do it.

When I want to manually play in some new notes on an existing midi track, the second I hit "Record", Logic slices my track and deletes everything underneath the new recording. It won't merge, or overlap, and any of the things it usually does. I've read some forums and changed various settings, but nothing makes any difference.

All I want to do is manually play in a drum fill at the tail end of my song. Not only is Logic erasing the existing drum track underneath but, the new notes I've recorded play back too slow.