That message means that one or more cells in that row belongs to an array of formulae, spanning an area that includes the row that you want to delete.
Look at the formulae in that row, and look for a formula that is surrounded by { } ( curly brackets ), as this indicates arrat formulae. Select the cell containing the array formula, and press Ctrl-/ , this will highlight the area covered by the array. You will need to delete the array before being able to delete the row.
Cheers, Glenn.