Smart Array 641 unreliable on ML370G4 - what to replace it with?

I have an ML370G4 which has been having problems recently with random freezes (current MTBF 2 days), and I notice that when it is frozen, one of the status LEDs (the rightmost of 8, marked MSB) on its Smart Array 641 controller is turned amber, so I'm assuming I need to replace that board. First, am I right? Second, that particular controller seems to be discontinued for a long time, so does anybody have any suggestions as to what I should replace it with?

Thanks for any help.