I am pleased to report that by taking relatively drastic measures, the 
USB 3 issues I have been experiencing with SL 6 have been solved.

Using kernel-2.6.38.6-26.rc1.fc15.src.rpm

I built and installed using rpmbuild and the SL 6 gcc 4.4 environment:

kernel-2.6.38.6-26.rc1.el6.x86_64.rpm
kernel-devel-2.6.38.6-26.rc1.el6.x86_64.rpm

Using these rpm files, the machine boots, the Nvidia 
NVIDIA-Linux-x86_64-270.41.19.run file produces a kernel module for the 
video card works under X11 (both Quadro FX 570 for video and Tesla C2070 
for computation) ,
VirtualBox builds its modules and runs MS Win XP Pro, a USB 2 device (a 
flash drive) with a MS file system is readable under MS Win XP, and the 
USB 3 external harddrive is seen and automounts displaying the same file 
system behavior seen under
kernel-2.6.38.6-26.rc1.fc15 within SL 6 as well as under OpenSUSE.  When 
the same USB 2 device is detached from VirtualBox, the filesystem 
automounts under SL 6 on the Linux host size.  Also, the fuse-ntfs 
mounting of a MS NTFS filesystem works and the drive seems readable and 
writeable.   (Aside:  my machine has a 160.0 GByte HP OEM harddrive in 
it that had MS Win XP HP installed -- this is NOT the file/filesystem I 
use for VirtualBox, but is mostly used as a test to verify that I have 
full NTFS access if I were to need it.)

My next endeavor will be to find a production (not rc) version of the 
above kernel and redo the process.

If anyone wants/needs these RPMs, please let me know.   Is there a 
reputable public site upon which one post such binary files for others 
to use?  I do not want to grant FTP access to my machine.  In a pinch, I 
should be able to post these to my personal web site at my university 
and one could get access by that means.  Be aware that I have not yet 
extensively tested this kernel nor have I verified the stability of it 
-- if the machine crashes/panics, I will report this to the SL list.

Yasha Karant

Thus, I conclude that the current and rolling SL 6 x86-64 kernels do not 
properly support all common USB 3 external harddrives and control 
interfaces.  I have not tested any other USB devices.