I've never encountered this problem before. Post some screen shots.

when executing in VBA (open report or print report via vba command) there is no error message, but only the listboxes stopp getting updated after some 17/18 days (counts). In  case I open the report manually, the error message 'cannot open anymore databases' appears 24/25 times, which is the diference to 42 (total number of listboxes). So for me it looks like acccess is opening seperate connections for every single listbox.

Is your database split?

yes the database is split into frontend and backend.

i've tried to use a subform in the report and filling the listboxes (value lists) via vba, but then when i try to open the report via docmd.openreport "...", acViewNormal i get the following error message: Run-time error '2501': The OpenReport action was canceled. On the other hand I can open the report by doubleclicking it.

Try putting the backend file on the local PC and see if you still get the same issue.

I have had this problem a couple of times when creating a accde executable.  Each time the problem has been resolved by finding where you have created an event where there is no code in The event to execute.

The easiest way I have found to find this event is create a new database and after moving your tables and queries start moving your forms one by one or in small numbers and create your executable after each move.  When you get the connections error look for the event/s in that form or report.  Delete The code and resave as a executable.   It should now create the executable.  Continue moving small numbers of forms/reports extra and creating executables until you have them all across and the complete database up and running as the accde file.

Thank your Ronald, figured out what happened. I had an empty 'detail' section in the report therefore the error message came up..

My pleasure, 1st time I've been able to help someone to resolve a issue with MSAccess.  I find this issue very interesting as although having a Sub routine/event somewhere in your code which doesn't execute any code as sloppy coding it shouldn't crash creating a executable.  You would think the application would go into the routine and straight out again. Runtime (accdb) works fine with these empty subroutines/events.