I was just pulling my hair out trying to get MySql.Data 5.0.7.0 to work in my ASP.NET application.
I followed the instructions I found elsewhere on the forum about adding the <runtime><assemblyBinding>...etc section to my web.config file, however it was still not working. It was still looking for 5.0.3.0, ignoring my runtime attribute.
Finally, after many google searches, I came accross this:
http://aspadvice.com/blogs/ssmith/archive/2006/11/15/AssemblyBinding-in-Web-Config-and-XMLNS.aspx
I followed the instructions and removed the xmlns="http://schemas.microsoft.com/.NetConfiguration/v2.0" from the <configuration> element.
After I did this it worked falwlessly.