For those who may run into the same problem....
I upgraded this computer to Vista from XP. In the process, it transferred all of my XP tasks to the Vista Task Scheduler. However, some of those tasks weren't compatible with Vista's Task Scheduler. To fix the problem, go into your Windows directory (usually C:\Windows\system32\Tasks) and make a backup of any tasks that say they were created before you upgraded to Vista and send those backed-up files tot he desktop or somewhere where you know they are located. Then delete the files in the Tasks folder. Open up Task Scheduler and see if you get the error message. If not, then you can add each task back to the Tasks folder one by one to see which one is causing the problem. For me, it was UniBlue's SpeedUpMyPC task.
Vista Home Premium SP1 x86, Dell E510 Pent D 820, 2GB RAM, ATI X1650 Pro
Recently, I went into the Task Scheduler to create a new task for backing up some things. Went through the menus and clicked Finish to save the task. I went to my Task Library and got a "Catastrophic Error (Exception from HRESULT: 0x8000FFFF (E_UNEXPECTED)). Once in the Library, there are no tasks listed and I am then not able to create any other tasks. If I do, it says Task Scheduler is not running. However, I go into Comp Management > Services and see that it is running.
If I exit Task Scheduler and go back into it, I am again able to create a task. Still no access to the Library without an error. So I try again to create my same backup task and it ends up saying there is already another task with that name. (The one I first created above.) So, I can't view any of my tasks and have a catastrophic error on my hands. I've searched the web but haven't found any solution. I tried doing a chkdsk to see if something needed repaired, but everything was fine.
Thanks for any ideas you might have.