syslog fills with messages due to empty SD card slot.

Every 40 seconds or so, something like the following is printed in the syslog.

Apr 29 12:15:28 dellie-linux kernel: [12359.705257] sd 6:0:0:0: [sdb] Test WP failed, assume Write Enabled
Apr 29 12:15:28 dellie-linux kernel: [12359.707626] sd 6:0:0:0: [sdb] Asking for cache data failed
Apr 29 12:15:28 dellie-linux kernel: [12359.707634] sd 6:0:0:0: [sdb] Assuming drive cache: write through

I have a Dell laptop. sdb is probably my sd card reader slot. It's normally filled with a fake plastic protective card.

If I stick an actual sd card in the slot, the message logging goes away. Even after I pull the real card out, without unmounting it, the messaging doesn't come back. Once the system knows that the card's unmounted, the messages return.
---
AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.23.
ApportVersion: 2.0.1-0ubuntu7
Architecture: amd64
ArecordDevices:
 **** List of CAPTURE Hardware Devices ****
 card 0: Intel [HDA Intel], device 0: STAC92xx Analog [STAC92xx Analog]
   Subdevices: 2/2
   Subdevice #0: subdevice #0
   Subdevice #1: subdevice #1
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: chris 3153 F.... pulseaudio
Card0.Amixer.info:
 Card hw:0 'Intel'/'HDA Intel at 0xf6afc000 irq 47'
   Mixer name : 'IDT 92HD71B7X'
   Components : 'HDA:111d76b2,102802aa,00100302'
   Controls : 24
   Simple ctrls : 15
DistroRelease: Ubuntu 12.04
HibernationDevice: RESUME=UUID=656d1e1f-5a61-478c-b0f5-83de3100c497
MachineType: Dell Inc. Inspiron 1545
Package: linux (not installed)
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: root=UUID=9c0edb3e-d193-44ce-829f-858ced0747b2 ro acpi_sleep=old_ordering quiet splash resume=/dev/sda5
ProcVersionSignature: Ubuntu 2.6.38-13.56-generic 2.6.38.8
RelatedPackageVersions:
 linux-restricted-modules-2.6.38-13-generic N/A
 linux-backports-modules-2.6.38-13-generic N/A
 linux-firmware 1.79
SourcePackage: linux
Tags: precise precise
Uname: Linux 2.6.38-13-generic x86_64
UpgradeStatus: Upgraded to precise on 2012-04-28 (1 days ago)
UserGroups: adm admin cdrom dialout libvirtd lp lpadmin plugdev sambashare
WifiSyslog:
 Apr 30 08:05:05 dellie-linux wpa_supplicant[1492]: WPA: Group rekeying completed with 20:76:00:07:b0:d4 [GTK=CCMP]
 Apr 30 09:05:04 dellie-linux wpa_supplicant[1492]: WPA: Group rekeying completed with 20:76:00:07:b0:d4 [GTK=CCMP]
WpaSupplicantLog:

dmi.bios.date: 12/07/2009
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A14
dmi.board.name: 0G848F
dmi.board.vendor: Dell Inc.
dmi.chassis.type: 8
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvrA14:bd12/07/2009:svnDellInc.:pnInspiron1545:pvr:rvnDellInc.:rn0G848F:rvr:cvnDellInc.:ct8:cvr:
dmi.product.name: Inspiron 1545
dmi.sys.vendor: Dell Inc.