Loading the layout when the data source is null will result in the grid discarding most of the layout, since no bands or columns exist in the data source.  Only properties on the DisplayLayout (including DisplayLayout.Override) will be kept - any column-specific or band-specific data will be lost.  Instead, set your data source first, then load the layout.

Are you assigning your grid's data source in Form_Load?  If so, that provides an ideal way to ensure it happens when the form is loaded.

Otherwise, add a boolean property to your form, and initialize it to false.  After you set the grid's data source, check the flag - if it's false, load the layout and set the flag to true.  The next time you hit where you're setting your data source, the flag will already be true, and so you'll know not to load the layout.