8.2-PRERELEASE generating warnings re my hard drive

[Charlie Kester]

I'm running 8-STABLE, i386 architecture, and yesterday I updated to the
latest version with cvsup.

After installing the kernel and rebooting, I see the following messages on the console:

ad4: WARNING - SETFEATURES SET TRANSFER MODE requeued due to channel reset                                                                                                         
ad4: interrupt on idle channel ignored
ad4: WARNING - SETFEATURES SET TRANSFER MODE requeued due to channel reset
ad4: interrupt on idle channel ignored

(repeated several times, and then the following:) 

ad4: WARNING - SETFEATURES SET TRANSFER MODE taskqueue timeout - completing request directly 
ad4: 238475MB <Seagate ST3250410AS 3.AAF> at ata2-master UDMA100 SATA 1.5Gb/s

(shortly afterwards, I see this:)

Trying to mount root from ufs:/dev/ad4s1a
ad4: WARNING - READ_DMA requeued due to channel reset LBA=33963227
ata2: FAILURE - already active DMA on this device
ata2: setting up DMA failed
g_vfs_done():ad4s1f[READ(offset=12103825408, length=2048)]error = 5
ad4: WARNING - READ_DMA requeued due to channel reset LBA=705199
ata2: FAILURE - already active DMA on this device
ata2: setting up DMA failed

(which then repeats many times with different LBA and offset values.)

Similar messages appear after bootup is completed and I've logged in.
They seem to appear whenever any process accesses the hard drive.

I reverted back to my previous build of the kernel, dated 3 Feb 2011,
and these messages no longer appear.

smartctl reports that the drive is running without any errors or
incipient failures.

So my question is, what's going on here?  Is this something I should
worry about?  If it's a problem with my kernel config, what parameters
should I be looking at?

Motherboard: Intel DM510 with builtin IDE controller.