Problem with Image deserialization

I developed my website on my local machine, in VS 2010 with ASP.NET 3.5. It worked fine, and then I uploaded it. Everything still works, except for the pages in the "members" directory. When I turned on debugging, I got this error:

[FONT=Arial, Helvetica, Geneva, SunSans-Regular, sans-serif]
Exception Details: System.ArgumentException: Parameter is not valid.

Source Error:

Line 41: using (MemoryStream ms = new MemoryStream())
Line 42: {
Line 43: image.Save(ms, codec, ep);
Line 44: return ms.ToArray();
Line 45: }[/FONT]

This page is an ASP.NET handler, and what it does is retrieve a user's image from the database. You can see this error at http://www.sitechsmart.com/pichandler.ashx?username=dobry. It worked on my computer, but not when I uploaded. The source is exactly the same, so I don't know what could be wrong. Any help would be greatly appreciated!