After the last cvsup and portupgrade, sylpheed-claws was now known as claws-mail. Now gpg didn't work anymore. Some googling mentioned that the program tries to use gpg-agent. So I changed my configuration accordingly and installed pinentry-qt, a graphical passphrase dialog utility.

This is my gpg-agent.conf. It belongs in your local .gnupg/-directory:

pinentry-program /usr/local/bin/pinentry-qt
default-cache-ttl 3600

You also have to add use-agent to your local gpg.conf (probably in .gnupg/, too).

To start the gpg-agent, add `evalgpg-agent --daemon`` to your.login`-file or wherever you need. By now your gpg-support should be functional (again).