Vista - Flash Memory Card Reader - 16 GB SD Card - Won't Read

Hi:

I have a Ativa brand (Office Depot store brand) SD/SDHC card reader. On my
home computer, which is a HP dv9925nr 4GB RAM running Windows Vista Home
Premium 64-bit, my card reader causes my machine to run very slowly when I
insert a Patriot memory 16 GB SDHC card in it. It runs up to 8 GB cards OK.
The computer does eventually recognize it but it runs too slowly for me to
open files. Fortunately I can use the built in SDHC card reader on the
computer but its the point.

Now, at work, I use a Dell notebook computer that runs XP Professional.
That one accepts the card reader / 16 GB SDHC card just fine. So it isn't
the card reader or any capacity limitations or anything. I'm thinking its
some kind of driver missing or other conflict with Vista 64-bit.

Incidentally, a slightly older but very similar type card reader from Ativa
does run this 16GB card OK. Also, I bought a 2nd one - same kind - and it
also has the same problem. So its not isolated. Ideas?