microsoft excel 2010 - Getting Application-Defined or Object defined error

I'm working with multiple sheets in my macro, for this particular code I'm just using 2 sheets. One to get the information, and the other to print the data.

Here's the part of my code with the problem:

Sheets("Layout").Select

For q = 1 To Z
    For i = 5 To 15
        For j = 5 To 785
            If Cells(j, i) = Salidas(q) Then
            Despejes(q, 1) = j
            Despejes(q, 2) = i
                x = j
                y = i
                u = i
                k = j
                aux = 0
                suma = 0
                'Enocntrar el Tier1
                Do While Cells(k, u) <> u - 4
                    k = k + 1
                Loop
                Do While Cells(k - 1, u + 1) <> ""
                        aux = aux + 1
                       u = u + 1
                Loop


                For b = y + 2 To y + aux
                p = k - 1
                    For a = 1 To 5
                       If Cells(p, b) <> "" Then
                            suma = suma + 1
                        End If
                        p = p - 1
                    Next
                Next

                For a = k - 5 To x
                    If Cells(a, y + 1) <> "" Then
                        suma = suma + 1
                    End If
                Next

                For t = k - 5 To x - 1
                    If Cells(t, y) <> "" Then
                        suma = suma + 1
                    End If
                Next

                g = x
                Do While Cells(g, y) <> ""
                    Cells(g, y) = Cells(g - 1, y)
                    g = g - 1
                Loop

        End If
        Despejes(q, 3) = suma
        Next
    Next
Next

In the first Do while is where the error is showing and I have no idea why.