Here's something that doesn't sound good regarding these controllers: http://lists.us.dell.com/pipermail/linux-poweredge/2005-March/019975.html
Adapters with the following PCI vendor ID and device ID pairs are not supported by the megaraid_mbox driver:
The lspci -n command can be used to display the IDs for adapters installed in a particular machine. Products with these IDs are known by (but not limited to) the following model names:
* Dell PERC (dual-channel fast/wide SCSI) RAID controller
* Dell PERC2/SC (single-channel Ultra SCSI) RAID controller
* Dell PERC2/DC (dual-channel Ultra SCSI) RAID controller
* Dell CERC (four-channel ATA/100) RAID controller
* MegaRAID 428
* MegaRAID 466
* MegaRAID Express 500
* HP NetRAID 3Si and 1M
Both Dell and LSI Logic have indicated that they no longer support these models in the 2.6 kernel.
You can boot Knoppix and see if you fall into this category.