vacuum problems

Hi,
 I'm writing a logfile processing app.
 everytime I processed a logfile and moved the information into a
relation, I try to vacuum it. But after a while (after the nth logfile)
vacuum freezes with the following message:

NOTICE:  BlowawayRelationBuffers(annex_log, 7): block 7 is referenced
(private 0, last 0, global 1)
FATAL 1:  VACUUM (vc_rpfheap): BlowawayRelationBuffers returned -2

 What went wrong?

    Thanks in advance

--------------------------------------------------------------------------------
Sebestyén Zoltán <szoli@netvisor.hu>    I'm believing that the Holy Spirit is
                    gonna allow the hand, and the foot, and
MAKE INSTALL NOT WAR            the mouth, just to begin to speak, and
                                        to minister, and to heal coordinated by
                    the head.

I use UNIX because reboots are for hardware upgrades.

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