Problem with KMail

[Marc]

Hello,

I have a problem with GPG.

When I receive an email encrypted in my inbox and that I want to see it I
have the message:
Encrypted message (decryption not possible)
Reason: Crypto plug-in "openpgp" could not decrypt the data.
Error: Bad passphrase

The problem it's that it does not ask me the password for decrypt the
 
I installed pinentry, but that doesn't change.  
Here lines in gpg.conf:

# Passphrase agent
#
# We support the old experimental passphrase agent protocol as well as
# the new Assuan based one (currently available in the "newpg" package
# at ftp.gnupg.org/gcrypt/alpha/aegypten/).  To make use of the agent,
# you have to run an agent as daemon and use the option
#
# use-agent
# 
# which tries to use the agent but will fallback to the regular mode
# if there is a problem connecting to the agent.  The normal way to
# locate the agent is by looking at the environment variable
# GPG_AGENT_INFO which should have been set during gpg-agent startup.
# In certain situations the use of this variable is not possible, thus
# the option
# 
# --gpg-agent-info=<path>:<pid>:1
#
# may be used to override it.

default-key  A13270E3
use-agent




I have create gpg-agent.conf in /.gnupg/ with :

pinentry-program /usr/bin/pinentry-qt
no-grab
default-cache-ttl 1800


Do I have to change something?  
And what?  

Thank you

Marc.