Assembly in host store has a different signature than assembly in GAC

I have added a third party dll (Extreme.Numerics.Net20.dll to my sql server assemblies). I then opened by VS 2008 project and added that assembly as a reference. Then I built and released my project and it created a PowerstatRegression.dll. Then I add that assembly to SQL Server as well. But when I run my code, I still get this:

Error message: System.IO.FileLoadException: Could not load file or assembly 
'Extreme.Numerics.Net20, Version=3.6.10055.0, Culture=neutral, 
PublicKeyToken=9e513770f58567b2' or one of its dependencies. Assembly in host store has a 
different signature than assembly in GAC. (Exception from HRESULT: 0x80131050) File name: 
'Extreme.Numerics.Net20, Version=3.6.10055.0, Culture=neutral, 
PublicKeyToken=9e513770f58567b2' at 
PowerStatRegression.matrix.MatrixHandler.MultiplyMatrixByArray(Double[][] a, Double[] b) at 

Why is this happening? Everything builds correctly with no errors.

Change your CREATE ASSEMBLY to ALTER ASSEMBLY and rerun that on the server, that will update the GAC.