Hello,
looking to ERP 6.0 Online help, the GR time should be considered: Scheduling: In-House Production: Calculating Basic Dates http://help.sap.com/saphelp_erp60_sp/helpdata/en/88/abce5314894208e10000000a174cb4/content.htm
If your problem is related to any special R/3 customizing or an product error (maybe in combination with the CS Add-on), I can not judge.
You are using SAP R/3 4.6C release with the Cable Solution add-on, which is out of maintenance.
Product Version SAP R/3 4.6C
End of Mainstream Maintenance: 31.12.2006
End of Extended Maintenance: 31.03.2013
Source: Product Availability Matrix
In general, you can create an SAP error message / ticket. Due to end of maintenance you will be charged by hour for a root cause analysis.
See also details in SAP note: 52505 - Support after end of mainstream/extended maintenance
http://service.sap.com/sap/support/notes/52505
Greetings, Stefan