Recently I did experience a very strange problem related to GnuPG. My mail program, KMail, stopped responding as soon as I did try to open a PGP signed mail or even if I did write a mail. I tracked the problem down to GnuPG. Some long-gone process didn’t release his lock and caused strange troubles.
After removing the locks (pubring.gpg.lock and .#*) it did work fine again.