Could not load file or assembly itextsharp Version4.1.2.0

Hi

I tried to export a grid view to pdf using iTextSharp.

When i build the program it does not leave me any exception.

But when i tried to run the program and click on "Export to PDF" button, it leaves me with an following exception  saying

"Could not load file or assembly 'itextsharp, Version=4.1.2.0, Culture=neutral, PublicKeyToken=8354ae6d2174ddca' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)"

I can guess that it is not a dll error.

Can any one help me in this issue.

Thanks in advance.

Cheers.