Deserialization Error: "Unable to find assembly"

I get the following error when I attempt to deserialize a structure on the client software. What does this mean I have the declaration of the structure exactly the same in a module named exactly the same in both peices of software.

Unable to find assembly 'Server v1.0, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null'.

.NET Development25

Notes:

I have my structures delcared in a module
The serialization and de-serialization takes place in a class
And I have made sure System.Runtime.Serialization is imported on both the module and the class