Issues with Image class in C# dll

So I'm working on a game where we're decoding a custom file format. I need to be able to save using the C# Image class. I've stripped down the code and found that unity 3 (and 2.6) crashes when I try to do the following.

        Image ImageOne = new Bitmap(FilePath);
        Image ImageTwo;
        MemoryStream AStream = new MemoryStream();
        ImageOne.Save(AStream, ImageFormat.Tiff);
        ImageTwo = new Bitmap(AStream);
        ImageTwo.Save(@"C:\NewPic.jpg");

Unity crashes on the ImageOne.Save call. My dll is compiled using .NET 3.5 and I've got a test app using 3.5 that runs and the code works. Has anyone encountered this and found a solution or a way around it?

Submit a bug report to support@unity3d.com