strange, that message doesn't even refer to libata, it looks more like the nforce2 ide driver. e.g. ide1 on my system is the second channel of it.
libata refers to channels as ata0, ata1 etc. Maybe try a kernel with out nforce2 ide support, just to rule it out. Then on a kernel with nf2 ide support it would be helpful to pass at boot time, hdc=none hdd=none, which would disable the second channel.
NFORCE2: IDE controller at PCI slot 0000:00:09.0
NFORCE2: chipset revision 162
NFORCE2: not 100% native mode: will probe irqs later
NFORCE2: 0000:00:09.0 (rev a2) UDMA133 controller
ide0: BM-DMA at 0xf000-0xf007, BIOS settings: hda:DMA, hdb:DMA
ide1: BM-DMA at 0xf008-0xf00f, BIOS settings: hdc:DMA, hdd:DMA