I could re-produce that error simply by running the app and once it is completely settled, closing it. Even for that I have spend several hours and tracked problem down to specific database operation(s). I use UniDAC and suspected that their native DBF (dBase) support might be the problem.
I have remarked relevant code lines and continue my development. At some point, I needed these database operations and removed their remarks. It is very strange that after that error is not each time but random. I am not getting that error anymore, now. I do know same lines are called at each time and they are doing exact same things.
If it appears again, I am going to directly check these database operations though.
Thanks for the help.