Perlin Noise acting strange - vb.net

Question

I am trying to implement a 2D Perlin Noise in VB.Net. I've spent the whole day searching for sources that explain the subject and one of the most notable was this article by Hugo Elias
Most of the implementation went well. On the exception of a very important part that did not seem to work in VB.Net, causing overflows.
function Noise1(integer x, integer y)
n = x + y * 57
n = (n<<13) ^ n;
return ( 1.0 - ( (n * (n * n * 15731 + 789221) + 1376312589) & 7fffffff) / 1073741824.0);
end function
In VB.net I translated it to
Private Function Noise(tX As Integer, tY As Integer) As Double
'Return a double between -1 & 1 according to a fixed random seed
Dim n As Integer = tX + tY * 57
n = (n << 13) Xor n
Return (1.0 - ((n * (n * n * 15731 + 789221) + BaseSeed) And &H7FFFFFFF) / 1073741824.0)
End Function
Which cause overflows.
Since the idea seem to be to simply generate a fractional number between -1 and 1. I've made this little function which create a Integer Number based on the coordinates and BaseSeed. BaseSeed(999999) being the base for every noise I'll create in this particular part of my game.
Private Function Noise(tX As Integer, tY As Integer) As Double
Dim tSeed As Integer
tSeed = WrapInteger(789221, BaseSeed, (tX * 1087) + (tY * 2749))
RandomGenerator = New Random(tSeed)
Return (RandomGenerator.Next(-10000, 10001) / 10000)
End Function
WrapInteger simply makes sure that the number will always be in the range of an integer, to avoid overflow errors.
Public Function WrapInteger(ByVal Lenght As Integer, ByVal Position As Integer, ByVal Movement As Integer) As Integer
Lenght += 1
Return ((Position + Movement) + (Lenght * ((Abs(Movement) \ Lenght) + 1))) Mod Lenght
End Function
When I fire it up with a Persistence of 0.25, 6 Octaves and a starting frequency of 2. this is what I get. This is a 128x128 pixel bitmap that I scaled.
Result
Anyone have an idea of why it would be so linear? When I look at this picture I have the feeling that it's not far from the truth, as if it only worked in 1D. All suposition.
Below you will find my entire PerlinNoise Class. I think the rest of it is just fine, but I added it for reference purpose. Beside, I haven't been able to find a single VB implementation of Perlin Noise on the internet. So I guess if I can fix this one, it might help others. There seem to be alot of question about Perlin noise malfunction on StackOverflow
Public Class cdPerlinNoise
Private RandomGenerator As Random
Private BaseSeed As Integer
Private Persistence As Double
Private Frequency As Integer
Private Octaves As Integer
Public Sub New(tSeed As Integer, tPersistence As Double, tOctaves As Integer, tFrequency As Integer)
Frequency = tFrequency
BaseSeed = tSeed
Persistence = tPersistence
Octaves = tOctaves
End Sub
Private Function Noise(tX As Integer, tY As Integer) As Double
Dim tSeed As Integer
tSeed = WrapInteger(789221, BaseSeed, (tX * 1087) + (tY * 2749))
RandomGenerator = New Random(tSeed)
Return (RandomGenerator.Next(-10000, 10001) / 10000)
End Function
Private Function SmoothNoise(tX As Integer, tY As Integer) As Double
Dim Corners As Double = (Noise(tX - 1, tY - 1) + Noise(tX + 1, tY - 1) + Noise(tX - 1, tY + 1) + Noise(tX + 1, tY + 1)) / 16
Dim Sides As Double = (Noise(tX - 1, tY) + Noise(tX + 1, tY) + Noise(tX, tY - 1) + Noise(tX, tY + 1)) / 8
Return (Noise(tX, tY) / 4) + Corners + Sides
End Function
Private Function InterpolateCosine(tA As Double, tB As Double, tX As Double) As Double
Dim f As Double = (1 - Cos(tX * 3.1415927)) * 0.5
Return tA * (1 - f) + tB * f
End Function
Private Function Interpolate2D(tX As Double, tY As Double) As Double
Dim WholeX As Integer = CInt(Fix(tX))
Dim RemainsX As Double = tX - WholeX
Dim WholeY As Integer = CInt(Fix(tY))
Dim RemainsY As Double = tY - WholeY
Dim v1 As Double = SmoothNoise(WholeX, WholeY)
Dim v2 As Double = SmoothNoise(WholeX + 1, WholeY)
Dim v3 As Double = SmoothNoise(WholeX, WholeY + 1)
Dim v4 As Double = SmoothNoise(WholeX + 1, WholeY + 1)
Dim i1 As Double = InterpolateCosine(v1, v2, RemainsX)
Dim i2 As Double = InterpolateCosine(v3, v4, RemainsX)
Return InterpolateCosine(i1, i2, RemainsY)
End Function
Public Function PerlinValue(tX As Double, tY As Double) As Double
Dim Total As Double = 0
Dim Frequency As Double
Dim Amplitude As Double
For i = 0 To Octaves - 1
Frequency = Frequency ^ i
Amplitude = Persistence ^ i
Total = Total + (Interpolate2D(tX * Frequency, tY * Frequency) * Amplitude)
Next
Return Total
End Function
Public Function ScaleNoise(ByVal tX As Double, ByVal tY As Double, ByVal OutputLow As Double, ByVal OutputHigh As Double) As Double
Dim Range1 As Double
Dim Range2 As Double
Dim Result As Double
Range1 = 1 - -1
Range2 = OutputHigh - OutputLow
'(B*C - A*D)/R1 + n1*(R2/R1)
Result = (((1 * OutputLow) - (-1 * OutputHigh)) / Range1) + ((PerlinValue(tX, tY) * (Range2 / Range1)))
If Result < OutputLow Then
Return OutputLow
ElseIf Result > OutputHigh Then
Return OutputHigh
Else
Return Result
End If
End Function
End Class