Could not load file or assembly Microsoft.Practices.EnterpriseLibrary.Common, Version=4.1.0.0 ASP.NET 4.0

Question

Platform : ASP.NET 4.0
Application : A website project with a Datalib ClassLibrary attached to it
Dependencies:
IIS: 5.1(local and IIS 7.0 online)

I am getting the error at localhost. I haven't checked online yet.
The whole thing was working at ASP.NET 3.5 and now when i upgraded to ASP.NET 4.0 I get the following error.

The Stack Trace is

At VisualStudio 2010, the error is

This is not happening everytime.
The first runs always show this error.

What could be wrong?

Answer 1

I guess it's looking in the wrong place for some reason... try adding this assembly to the server GAC and remove it from the BIN folder.