Hello Eric,
Check the package of the class of Overwrite method (CL_ERP_SWITCH_CHECK), it most probably involves a switch which is turned off.
This is also the reason why you cannot set a breakpoint because this coding will not be executed at runtime.
As Uwe mentioned, you can switch-on the business functions associated with the switch but be careful because this business function is not reversible, therefore cannot be switched off.
See also precautions that have to be taken when switching on a business function on the Help Portal:
http://help.sap.com/saphelp_nw70ehp1/helpdata/en/de/899442047b0831e10000000a1550b0/content.htm
Regards,
Pascale Boyer
SAP SFW Dev Support