Today I suddenly got this error when I tried to open a task:

The "TTask.Create - CreateDrive - Invalid source device type!" error.
Both trying to open Task.prm and Task.bak files gave this error, yet I could open other tasks just fine (I know others had this issue after a drive letter changed, etc.).
What I did to fix it was as follows:
Problem solved!

The "TTask.Create - CreateDrive - Invalid source device type!" error.
Both trying to open Task.prm and Task.bak files gave this error, yet I could open other tasks just fine (I know others had this issue after a drive letter changed, etc.).
What I did to fix it was as follows:
- Create a new task using same parameters
- Generate head map then close the task
- Copy over all imgXXXXX.bin files and the map.bin file
- Reopen the new task, right click on the map, and select "Recalc"
Problem solved!