@Ian971 –
I am running 64-bit Windows 7 with Visual Studio 2010. No other project that I reference uses SharpZipLib.
I didn’t use any Nuget package. Just downloaded the zip file from Codeplex. It only consists of the two DLLs and a .pdb file.
I added a reference to the DLLs in my project, which happens to by a SSIS script task.