Version:           1.8.2 (using KDE 3.4.2, compiled sources)
Compiler:          gcc version 3.3.6
OS:                Linux (i686) release 2.4.31

using kmail 1.8.2 which comes with slackware 10.1. By default, pgp encryption seems not to work.
- created key pair with kgpg, used it to send encrypted email to myself (smtp & pop servers)

- in preview window, reported "Encrypted message (decryption not possible)
Reason: Crypto plug-in "openpgp" could not decrypt the data.
Error: Decryption failed
  Encrypted data not shown.
  End of encrypted message"

- clicked on "body part" in description window, then clicked on unnamed (the encrypted mail body) selected "open with Kgpg" in dialog
- kgpg error dialog reports file not found
- clicked on it again, fails again, but kgpg error dialog reports "gpg: no valid openpgp data found\n[GNUPG:]NODATA 1\n[GNUPG:]NODATA 2\ngpg:decrypt_message failed"

- as root, replaced kgpg with script which dumps $@ to a log file, log file showed tmp file name in similar format to other tmp files, but not a valid filename. format was "/tmp/kde-kourama/msg.asc_[5NdWga].asc" only chars in brackets are different
- by default gpg-agent was not available, I d/led gnupg 1.9.9 and all needed support libs, compiled & installed everything, and added gpg-agent startup to file in ~/.kde/env, but behaviour is exactly the same before and after install.
-also, restarted kde a few times with different settings in kgpg (enable/disable gpg-agent, different default keys and servers, etc) no change in behaviour of kmail

doesn't seem to be encryption related at all, I can decrypt messages manually on the command line, mystery is why the temp files passed to kgpg are invalid.

other things that are running:kterm,kwallet,konqueror,kontact,klipper
hardware:thinkpad 390e laptop, usb mouse, ndiswrapper with linksys card
kernel: custom compiled, pretty much the same as a standard kernel with some unnecessary stuff compiled as modules, optimized for my cpu