I right clicked a dts package and scheduled it to run every two hours(for testing). Nothing happened. So, I right clicked and select "schedule package" to view my schedule, surprisingly I only saw default setting. My previous schedule was gone.
I used other sqlserver db and scheduled multiple dts packages. They worked fine.
If you right click a package and select 'schedule package', you are asking EM to create another schedule for the package. You will therefore see default setting to start with. When you schedule a package, EM creates a job. The job will have the same name as the package. You can verify or edit a previously created schedule by right clicking the job and selecting properties. The job will be under EM - management - SQL server agent - jobs.