Error messege: the selected task "{0}" no longer exists. to see the current task, click refresh

I spent a few minutes and tracked down the problem and a solution. The issue is a result of task files which exist in the Tasks folders which have no entry in (presumably) in the registry. Here's how I worked through the issue - will take some time, but it has cleared up the issue completely for me:

1. Open Task Scheduler and click OK when prompted with the error. It may seem like you are receiving the same error over and over, but this is really due to the number of tasks which are broken. Make a note of the number of times you are prompted with the the selected task "{0}" error. This is the number of task files that are out of sync with the registry.
2. Start with the first folder under Windows tasks (Task Scheduler(Local)\Task Scheduler Library\Microsoft\Windows) and select each folder in turn until you receive the the selected task "{0}" error. This folder contains files that are not in sync with the task scheduler.
3. Open Windows Explorer and navigate to the tasks file folder (%SystemFolder%\Tasks\Microsoft\Windows) and find the folder which corresponds to the folder in which you received the error.
4. For some tasks you will be able to determine which files need to be deleted by comparing the list in the Task Scheduler with the list of files in Explorer. Some tasks will only have a single file in explorer, or, in one case I had 2 and the first was missing. Once Task Scheduler encounters this error it will no longer display tasks so it makes the job of getting the two in sync a little more difficult. Once you have determined which files exist in the File Folder but do not exist in the Task Scheduler folder, delete those files.
5. IMPORTANT - Close and Re-open Task Scheduler. Once the error is encountered, Task Scheduler no longer displays the tasks so you need to close it and restart in order to continue your synchronization effort.
6. Continue to select folders in Task Scheduler under Windows tasks until you encounter the error again and repeat the process of determining which file exists on the file system, but not in Task Scheduler.

I had 6 files that were out of sync with what was displayed in Task Scheduler. Once I deleted all of the offending files, Task Scheduler fired up without issue.

Good luck.

Hi,

I had the same issue and here is what I did to solve my problem and hope it helps someone else in the future.  If you disabled the Disk Defrag Schedule, then go back and enable it.  It solved my problem and i've reported this bug to the Windows 7 team.