USB hard drive won't work on a USB 2 port but will on a USB 1.1 port.Why?

I recently purchased an external 300+ GB drive (a WDC WD32 00BB-00KEA0,
for what it's worth...). The hard drive isn't a problem when it's
running off one of the two USB 1.1 ports on the T23 ThinkPad with Vista
Ultimate (a post-beta near-RTM build 5840). That's the build that
Microsoft passed out free--along with a free unrestricted Office
Professional 2007--for attending its market launch in Detroit three
months ago.

Not wanting to have the drive run on USB 1.1, I picked up an EOL Adaptec
AUA-1422 (2 ports each of Firewire and USB 2) two days ago and attached
it to the empty CardBus slot. Then, I ran the external drive off one of
the two available USB 2 ports and attached a Belkin F5U237 7-port hub to
the other. The devices off the hub work OK, except for an older Chic
optical mouse. That wasn't much of a problem because I had an unused
Logitech LX 500 wireless keyboard/mouse that I just put into its initial
service. After a while with Driver Detective, I got it to work OK.

The rub is that Computer Management in Vista doesn't recognize the
previously formatted 40 GB partition, but instead the entire 295 GB
drive--as an unknown drive (no drive letter obviously--which previously
was 'H').

So, how do I get the hard drive recognized when running as USB 2.0? The
result is the same if the 1422 is used with both ports or with the hard
drive running alone without the 7-port hub.

Gary