After a Slackware upgrade, the IDEA plugin no longer worked on my Linux box. This plugin is needed if you want to be able to use GPG to encrypt/decrypt PGP files.

The problem manifested itself with the following error message:

gpg: invalid module `/usr/lib/gnupg/idea': gpg: undefined symbol: _idea_get_info

The solution turned out to be surprisingly simple: make sure you actually have the latest IDEA plugin installed! (See for an up-to-date link.) It appears that the code has undergone some changes, and the plugin I installed for 1.0.7 is no longer compatible with 1.2.2. A simple recompile will not suffice: you actually need the new code!