Hell Setwalker,
At the moment the force removal of the folder from Database is not very "forceful", it requires some conditions to be met, like it will try to save your disk image onto the desktop along with the tex doc containing the password for the disk image, this just to be sure you do not lose data.
But this also means that if he cannot find the disk image the removal will fail. In your case it is not entirely clear what does it miss, but in any case, obviously one of the conditions is not met and then it does not proceed with folder removal.
This will be fixed in upcoming version, with the option to unconditionally allow folder removal. Till then, please simply ignore it.
Thanks
Zsolt