could not access status of transaction 0

Hi all!

We seem to be getting this error (in german) once in a while on a rather
complex database:

FEHLER: konnte auf den Status von Transaktion 0 nicht zugreifen
DETAIL: kann Datei >>/var/databases/postgres/data/pg_subtrans/57DA<<
nicht erstellen: Die Datei existiert bereits

which roughly translates to

ERROR: could not access status of transaction 0
DETAIL: could not create file
>>/var/databases/postgres/data/pg_subtrans/57DA<<: File exists

and seems to be generated in backend/access/transam/slru.c
it looks like we got those(with changing filenames) about 5 times during
the last 2 months mostly during low-utilisation times (on this
particular database - not on the server itself).

The Server itself is a Dual AMD Opteron box running Debian Sarge/AMD64
with 64Bit Kernel and Userspace. PostgreSQL version is 8.0.5.
It might be interesting to note that we use slony to replicate a few
tables of this database to multiple slaves and according to our logs it
always was the slony-user connected to the database that triggered this
error.

Stefan