Error messages when generating new keys

[Olivier N.]

Hello!

I'm a newbie GPG user. I'm using Linux and GPG2.

When generating new keys, I get several error messages:

gpg: problem with the agent: Bad CA certificate
gpg: problem with the agent: Invalid card
gpg: Key generation canceled.

What mean “Bad CA certificate” and “Invalid card”?
How can I solve these problems?

Thanks in advance for your help!

Olivier