I made a TODO comment in one of my scripts, later on I re-organized my assets and moved the script to a new folder.
After that I had 2 instances of the comment in my task list, one in the original path, and one in the new path. Selecting the original or trying to delete it causes a file not found warning to pop up.
I can’t find a way to remove it. It obviously doesn’t break anything but its making my task list slightly confusing.
You can go to Tools > Options > Tasks, then remove TODO and confirm.
Then add it again from the same menu.
It does not look for old TODO tasks until you open the file in which it is located though.
I had the same issue as well. The info here helped: In monodevelop how can I clear out the Task list? - Stack Overflow
“try deleting the code completion database caches. On Mac you can find them in ~/Library/Caches/MonoDevelop-3.0/DerivedData, and on Windows they’re in AppData\Local\MonoDevelop-3.0\Cache\DerivedData.”
and
"Even in 4.0.1 (bundled with Unity3D) I ran into this issue. Nowadays these caches are per Assembly. So the file MonoDevelop.Ide.TypeSystem.ProjectCommentTags.cache has be deleted in the affected assembly’s directory. "
Though, on my Windows the folder was C:\Documents and Settings\ _YOUR_USER_NAME \Local Settings\Application Data\MonoDevelop-Unity-4.0\Cache\DerivedData
In any case, delete all MonoDevelop.Ide.TypeSystem.ProjectCommentTags.cache files. Monodevelop seem to have recreated them the next time I ran it and the Tasks are fine.