I have a track that shows up in my "Track Manager" but when I select the "Where to?" it is not listed. It appears to always be the first track (listed in track manager) that is missing.
Unfortunately they seem to be ordered by nearness to your current location, which means the first track is usually the one I want. This is causing me some real problems.
I am not the only one seeing this issue.
http://garmindakota.wikispaces.com/message/view/home/40209096
I don't remember this occurring in Version 3.80. Seems to have occurred after upgrading to Version 4.10.