Help with translating straight VB.net code to ASP.NET using VB

Greetings,
The following code works fine in a Windows app written in VB.Net, however it chokes in ASP.net written in VB:

Function GetImageFromURL(ByVal url As String) As Byte()
Dim wr As HttpWebRequest = _
DirectCast(WebRequest.Create(url), HttpWebRequest)
Dim wresponse As HttpWebResponse = _
DirectCast(wr.GetResponse, HttpWebResponse)
Dim responseStream As Stream = wresponse.GetResponseStream
Dim br As BinaryReader = New BinaryReader(responseStream)
Dim bytesize As Long = wresponse.ContentLength
Return br.ReadBytes(bytesize)
End Function

Private Sub Button1_Click(ByVal sender As System.Object, _
ByVal e As System.EventArgs) Handles Button1.Click
Dim img As New Bitmap( _
New IO.MemoryStream( _
GetImageFromURL( _
"http://yada.com/test.bmp") _
))
img.save("c:\file.bmp")
End Sub

It seems to choke on the following:

Dim img As New Bitmap( _
New IO.MemoryStream( _
GetImageFromURL( _
"http://yada.com/test.bmp") _
))
with the error of:
[ArugumentExecption: Invalid parameters used.]
System.Drawing.Bitmap..ctor(Stream stream)

Any suggestions?

Thanks