Choose save not working / 2 files opened simultaneously

One of my customers has the following problem:
After selecting choose save he gets a %SAVEFILENAME%-window with the following error message:
%SAVEFILENAME% funktioniert nicht mehr.
And he is unable to select and load any desired xlsc-files, except lastsave-files with his exe-file.
(only the options last save and original workbook are still working properly).

I guess the origin of the problem is, that my customer had two xlsc’s open simultaneously and saved them.

Question A: How can my customer get out of this situation? What can he do, to allow choose save again?
In former times wie could delete the *.dat file, which contained the filenames saved including path. But now an option allows to hide this information. This is the case with the exe of my customer. Where is the place where this information can be reset and how can this be accomplished?

Question B: Could Padlock please provide a feature or a suggestion to inhibit customers from opening several xlsc’s simultaneously which creates a number of further problems?

The .DAT file is stored in the location here: C:\Users\LOGIN\AppData\Roaming\XLSPadlock\UserApplication{Your app GUID}

We’ll check whether it is possible to limit the secure Excel instances to one instance only.