Its Lenovo HW, what do they say?

You're correct that this is a wide spread Vista problem and unlikely to be a
ThinkPad issue.  MS has, reportedly, acknowledged the problem but offers no
solution.  (http://www.theregister.co.uk/2008/04/16/vista_defender_sp1/)

Here's are a few things to try.

1.  Uninstall the  KB938371 update
(http://support.microsoft.com/?kbid=938371) if listed.  (This is the pre-SP1
MS update that is believed to be the cause of many of these problems.  It is
not, however, clear that removing it will necessarily undo the damage.

2.  The Cumulative update rollup for USB core components in Windows Vista
http://support.microsoft.com/?kbid=941600
may or may not be currently installed on your machine.  (It may have been
installed with or before SP1 and may have been removed with it's uninstall.)
Try to download and install it from the link above.   It has worked to fix
this problem for me in several cases.

3.   Look at the recommendation in this article.   In addition to forcing a
driver search to C:\Windows\winsxs try point a search to Windows\System32.
If this works, post back, for advice on  making a permanent fix.
http://www.tipandtrick.net/2008/usb-unknown-device-drive-issue-not-working-recog
nized-or-connected-error-after-upgrading-and-installing-vista-sp1/

I have now seen several cases of major problems caused by SP1 including one
completely trashed system (which was clean and stable beforehand).  What a
mess!  Please let me know if any of this helps.

I, too, have a T60 with the same Vista SP1 problem. However, in this case my
USB webcam works but when I attempted to add an external hard drive, the
system can not find the driver.

The Microsoft Knowledge Base this problem was solved with SP1 but it seems
that it actually may have worsened. Attempts to delete infcache.1 in hopes
that a rebuilt file upon reboot have not worked.

For me, I need access to my backup files on my USB hardrive but I have no
way to get to it.