KMail 1.6.2 always reports problems with signed S/MIME

None of the signed messages I receive can be verified.

KMail/gpg detects that it is a signed message and displays it accordingly.
The text body is readable but the signature verification always fails.

When I send signed S/MIME messages to myself the messages are displayed with:
"
Not enough information to check signature. [Details]
Status: No status information available.
"

Some signed mails from third parties cause this error:
"
Not enough information to check signature. [Details]
Status: Internal system error #0 occurred.
"
e.g. recent mails of Ingo Klöcker on the Aegypten mailing list.


In both cases the [Details] hyperlink does nothing.

The log file shows the following after I open one of these signed mails:

2004-07-19 21:54:39 gpgsm[4290] failed to create temporary file 
`/home/xyz/.gnupg/.#lk0x80733e8.linux.4290': File exists
2004-07-19 21:54:40 gpgsm[4290] Fatal: can't create lock for 
`/home/xyz/.gnupg/pubring.kbx'
2004-07-19 21:54:40 gpgsm[4291] ksba_cms_parse failed: EOF


I have:
SuSE 6.1
KDE 3.2.3
KMail 1.6. 2
gpg 1.2.4
gpgme 0.3.16
newpg 0.9.4




Any clue as to what might be wrong?