Unexpected error: The requested operation cannot be performed

[Slasher]

I'm wondering what this message actually means:

Unexpected error: The requested operation cannot be performed on a file with a user-mapped section open.

ags 3.2.1

[Khris]

WHEN did you get this error...?
While editing? While playing? What exactly did you do?

[Slasher]

I think I compiled and when to Run window mode and it popped up...

It was ok the next time.