OpenPGP card not working

[David Robertson]

Hello,
I've just bought myself a Gemplus/Gemalto GemPC twin USB smartcard
reader and a V2.0 OpenPGP card. I'm running Debian Squeeze. I've set up
udev rules as described here
http://www.gnupg.org/howtos/card-howto/en/smartcard-howto-single.html .
However, when I insert my card and type gpg --card-status I get (gpg 1.4.10)

gpg: selecting openpgp failed: ec=6.108
gpg: OpenPGP card not available: general error

Using gpg2 (2.0.14), I get

gpg: selecting openpgp failed: Card error
gpg: OpenPGP card not available: Card error

If i su into root, I get a different output for  gpg 1.4.10:

gpg: pcsc_establish_context failed: no service (0x8010001d)
gpg: card reader not available
gpg: OpenPGP card not available: general error

How can I fix this?
Thanks in advance,
David Robertson.