A generic error occurred in GDI+ - On specific server only - asp.net

Question

I have the following piece of code that turns an image into a byte array to store in the database.
Public Function Image2Bytes(ByRef aImage As Drawing.Image) As Byte()
Dim MemStream As New MemoryStream()
aImage.Save(MemStream, Drawing.Imaging.ImageFormat.Png)
Return MemStream.ToArray()
End Function
This works fine on our local server as well as some production servers. However, on some shared hosting servers, this gives a GDI+ error as described below:
Error: Exception of type 'System.Web.HttpUnhandledException' was thrown. > A generic error occurred in GDI+.:
Top Stack Trace:
System.Web.UI.Page.HandleError(Exception e)
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
System.Web.UI.Page.ProcessRequest(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
System.Web.UI.Page.ProcessRequest()
System.Web.UI.Page.ProcessRequest(HttpContext context)
System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)
Inner Stack Trace:
System.Drawing.Image.Save(Stream stream, ImageCodecInfo encoder, EncoderParameters encoderParams)
Common.Image2Bytes(Image& aImage)
EntityClass.Validate()
Logo.Page_Load(Object sender, EventArgs e)
System.Web.UI.Control.OnLoad(EventArgs e)
System.Web.UI.Control.LoadRecursive()
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
I've seen a lot of "Generic GDI+" errors here, but none of them solve this issue. For each solution I need to upload to a specific production server to test, as locally, there is no error.
Any ideas?