The scheduling granularity for the project is set to start and end all tasks on hour boundaries, but the locked start date for this task occurs on %1@ between hour boundaries.

To resolve this, do one of the following:

  1. Set this task's dates to automatic,
  2. Move the manual date earlier to the previous hour boundary, %2@, or
  3. Move the manual date later to the next hour boundary, %3@, or
  4. Change the project scheduling granularity to Exact Scheduling.