PowerEdge 2400 System Firmware Updates?

Hello,

I receive the following error message when the server(tag#FD3Y20B) boots 'System Firmware is Out of Date....Please Update Firmware'.

Which firmware is the message referring to?  I have the following firmware revisions installed;

ESM - 5.22

System Backplane - 5.24

I don't see any updated firmware on the Dell website.

Thanks,

Bill...