Possibly related (same subject, not in this thread)

• 2012-07-02 · [Bug 25832] kernel crashes when a mounted ext3/4 file system is physically removed · <hidden>
• 2011-09-17 · RE: [Bug 25832] kernel crashes when a mounted ext3/4 file system is physically removed · Alan Stern <stern@rowland.harvard.edu>
• 2011-09-16 · RE: [Bug 25832] kernel crashes when a mounted ext3/4 file system is physically removed · Alan Stern <stern@rowland.harvard.edu>
• 2011-09-10 · Re: [Bug 25832] kernel crashes when a mounted ext3/4 file system is physically removed · Ted Ts'o <tytso@mit.edu>
• 2011-09-04 · [Bug 25832] kernel crashes when a mounted ext3/4 file system is physically removed · <hidden>

Ted:

You also ought to look at this bug report and the follow-up thread.  
The symptoms are similar, although not exactly the same.

	http://marc.info/?l=linux-kernel&m=131504588401397&w=2
	([BUG] D state process after unplug and umount usb disk)

Alan Stern