You need to rectify that this issue is related to specific schedule task/tasks or with all schedule tasks. Like if you create a new schedule task, a simple one, say display output or send e-mail, generate excel etc. and then if you delete it, what happens then?
In this way, we will be able to rectify that this issue is not with specific schedule task/tasks.
Do you have admin rights? Also, let's say you use neo-cron.xml from a dev server that do not have any schedule task and if you use that neo-cron.xml, update it with your schedule tasks, what happens then?
Hope that helps
Thanks
VJ 