DeleteCommand, InsertCommand, UpdateCommand and connection string are correct. have not been changed since the time when everything worked. In addition, I created a new project on a fast where these parameters are the same and everything works.
I changed the system to 32bit and the problem is not resolved...
The problem is that I do not know what I did. I had not noticed the problem right away...
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I installed my database to Program Files. There was no problem with permission on Windows XP but there is on Windows 7
I have added manually permission to the installation folder. I think now how to add it automatically.