I´ve got the same problem. Good idea is to forward the task to somebody else so you don´t have to care about and the task is no longer disturbing.
Wich version of LC are you using?
I'm not sure but I think that it was a bug in LC 8.0.
Anyway, you can solve this problem by deleting terminated tasks from tb_task table.
ALC 8.2 version...
Strange, I thought that it was fixed...
Just remove terminated tasks from tb_task table.