Hi Michel,
the version at the client's site is probably compiled in release mode, which drops the line numbers. You can either compile in debug mode for testing or you can set the build properties for release. Right-click the project, properties make sure it's set to release configuration and under the build settings enable the "Generate Debugging Information" box. You'll need to deploy the .PDB files as well.
- Craig
"If you're not prepared to be wrong, you will never come up with anything original."
- Sir Ken Robinson