Simatic CP 5431 PROBLEM

Hello, I have a system that has Siemens HMI 'WinCC' station and S5-115U (CPU 944B). The communication processor on PC side is CP5613 & on PLC side CP5431. The mode of communication is FDL. The problem is that when I plug in the programmed EPROM & turn on the PS, CP5431 goes into the stop mode instead of the non-syncrone mode i.e. green (run) LED goes off & red (stop) LED stays. The program in the EPROM is an example program, which comes with WinCC, & I have used it before without any problem. Please reply soon. Thanks & best Regards Muhammad Asim Mumtaz