VS 2012 System.InvalidOperationException

I created a windows desktop app using VS2012 Express, targeting the .net 4.0 framework. I created an installer.exe using InstallSimple. I installed it and it runs good on my windows 7 computer.
However, when a client installed it onto their windows 7 computer, and he tried to run the application he got the following error:

Problem Signature 01: raven solver i.g.a.exe
Problem Signature 02: 1.0.0.0
Problem Signature 03: 521d3ca4
Problem Signature 04: Raven Solver I.G.A
Problem Signature 05: 1.0.0.0
Problem Signature 06: 521d3ca4
Problem Signature 07: 47
Problem Signature 08: e0
Problem Signature 09: System.InvalidOperationException
OS Version: 6.1.7601.2.1.0.768.3
Locale ID: 4105
Additional Information 1: 9a35
Additional Information 2: 9a3520fa7146de8e40feadec3bac1d07
Additional Information 3: 3a79
Additional Information 4: 3a79aed6da8544a505350df7fc1c558d

Any ideas?:confused: