[O] Logbook not working?

[Lawrence Bottorff]

I'm trying to create Logbook entries with C-c C-z -- which has worked fine in the past. But now whenever I try I get 

org-back-to-heading: Before first headline at position 1151 in buffer current.org

. . . i.e., my entry doesn't show up anywhere. What have I inadvertently messed up?

LB