Problem 1: i'm suspecting that the
Framework version with which you built the Application is heigher
than what client is using.
Solution 1: try to build your appliction with the
.NET Framework version.
Problem 2: You might be building your application with
X64 option in build settings.
Solution 2: change the
Platform Target of
the Application from
X86 from buid
settings and rebuild your application.