Error message in 6200 software

[nileshsurya 0]

hi thr u all plc ppl i have two PLC 5/40 cpu's in hotbackup configuration on a DH+ network with BCM modules. the engineering station for those PLC's is a computer with a KT card and 6200 series software .. now sometimes while going online i get a error message something like HPLC is disconnected or shutdown and in the whoactive window i get ????? against the name of the CPU. when i cycle power the CPU the error goes but again it comes after sometime this error message i get sometimes only and not everytime can anybody guide me as to what could be the problem it will be of gr8 help if sumbudy replies soon thnx in advance Regards NileshSURYA