It looks like a bug in Lazarus. In my case there was module named CreateUserPointsSetDialog and containing form class named as TCreateUserPointsSetDialog. At design time dialog form was displayed normally, project was compiled successfully but at run time form was displayed as empty without any controls. After a few attempts to find solution I had finished with renaming TCreateUserPointsSetDialog into TCreateUserPointsSetDlg. It somehow solved the issue.
I hit this issue when I created menu which was populated from OnUpdate handler of associated action. It was main menu item which didn’t have handler itself. As result this menu item was disabled every time after population.
Solution is to uncheck the DisableIfNoHandler flag.
Example was taken from the project fit