Unable to set Defraggler Scheduled Scan

This is not something that always happens, but from time to time, it happens on computers. I do not know what way to fix it just yet, & it seems to occur across all MS OS.

It does not seem to matter if there are service packs, no service packs, updates, or no updates.

Quite simply, it happens at times that a user simply cannot set a scheduled scan for Defraggler. I had it happen on a user machine that has Vista installed, although it has also happened on XP & 7 machines. I cannot remember the exact error, but it is similar to "Unable to set task". Right clicking & running the program as "administrator" has no effect.

I am not sure what causes this to happen, although I feel sure it is something that happens with Windows relating to some file/registry key getting corrupted or missing. Is there a way to change the way Defraggler schedules scans? Because of this bug, er, well, some users cannot set a scan schedule!

Would there be a way to have Defraggler either change how it set a schedule, or at least offer another option to set a scheduled scan? Such as letting Defraggler auto-start with windows, then check if it needs to defrag that particular day or not?

I am sure you coding gods can figure something out!

Maybe there is an easy fix for the scheduled task error that I am missing?

Thanks!