There is an entry in the REAL .INI file to handle the situation where you reset the windows layout - this will basically clear the register with the "default" the next time it is loaded. This only happens whenever you do Window->Default Layout
So, from the Apps pane of the Launch Pad, double click on DmDesigner2_7.ini (do NOT try to open it in the Windows folder via explorer!)
Look for the group
[AutoLoadPlacementReset]
CSelectProjectDlg=1
CConnectToPLCDlg=1
Make sure those are set to 1. If those are 0, then that would explain WHAT is happening (but not WHY those are 0).