This command should create a task that every minute runs the calculator windows application.
schtasks /Create /tn \"mytask\" /sc MINUTE /mo 1 /ru \"myuser\"
Probably because the task isn't running interactively. Add the '/it' option:
/IT
A value that enables the task to run interactively only if the /RU user is currently logged on at the time the task runs. The task runs only if the user is logged on.
Without the /it option, tasks run in session 0, which doesn't allow interaction with the user. For more information, do a web search for "Session 0 isolation".