strange problem with DMA

[dukeinlondon]

When I am trying to enable DMA for /dev/hda using hdparm -d1 /dev/hda

the disk operations freeze for a moment and I get that in syslogs :

Apr 8 00:17:41 localhost kernel:
Apr 8 00:17:41 localhost kernel: ide: failed opcode was: unknown
Apr 8 00:17:47 localhost kernel: hda: status timeout: status=0xd0 { Busy }
Apr 8 00:17:47 localhost kernel:
Apr 8 00:17:47 localhost kernel: ide: failed opcode was: unknown
Apr 8 00:17:47 localhost kernel: hdb: DMA disabled
Apr 8 00:17:47 localhost kernel: hda: drive not ready for command
Apr 8 00:17:47 localhost kernel: ide0: reset: success

Apr 8 00:14:07 localhost kernel: hdb: dma_timer_expiry: dma status == 0x41
Apr 8 00:14:07 localhost kernel: hdb: DMA timeout error
Apr 8 00:14:07 localhost kernel: hdb: dma timeout error: status=0x58 { DriveReady SeekComplete DataRequest }

It didn't use to be a problem in the past even with kernel 2.6.6 (custom debian image)

Any idea ?