Like Spod describes, this is likely the issue of having too many option ROM's.
Only one of the two (SCSI, IDE RAID) will POST, however, they will still both be detected & usable under Windows.
So, I suggest you decide which card you need POST access to, then move it closer to the AGP slot than the other one (SCSI or IDE). That will give priority to that card, but will still allow both cards to be visible under Windows.
I have the same issue with 3Ware Escalade 6200 and an Adaptec 29160N.
Hope that helps.