I have the same problem with a Dawicontrol DC-3410 (SIL3124-2). Two drives are attached to the onboard SATA ports.
If the RAID controller is inserted but no drives are plugged into it it boots fine, but connecting drives to the RAID controller prevents the machine from booting, although all drives (from the onboard controller and the ones attached to the DC-3410) are detected and listed in the D510MO BIOS boot order list. The only solution I found was disabling the RAID controller BIOS (by removing a jumper on the DC-3410 and therefore preventing the D510MO BIOS from seeing the drives) and booting from the internal SATA controller. The drives are later discovered by the linux kernel. Unfortunately the machine freezes after a while when the DC-3410 is connected, which I suspect it's the board's fault.
I am experiencing the same problem, with openSUSE 11.4 Linux 64-bit.
I flashed the D510MO motherboard to the latest BIOS (v5.42) and it does not fix the issue. My boot drive is connected to the motherboard's SATA connector. The RAID card I am using is an Addonics ADSA4R-E (4-port PCI-eSATA) with the Silicon Image SiI3114 chip, connected to an external disk array box with four SATA disks drives.
If the external disk array is connected and powered up when the system boots, it will get past the POST and the disk drives will appear in the eSATA BIOS list, but then it will hang when loading the grub bootloader. If there are no drives connected to the RAID card (or if the disk array box is powered off), the system would boot fine.
The Addonics card has worked perfectly on other motherboards, so it's not the problem.
A BIOS bug on the D510MO?
This issue has also come up in another forum: