vacuum fails - Mailing list pgsql-sql

vacuum fails with the following error:

NOTICE:  Rel beruf: Pages 18: Changed 0, Reapped 18, Empty 0, New 0; Tup
900: Vac 565, Crash 0, UnUsed 441, MinLen 60, .
NOTICE:  Ind idx_b: Pages 17; Tuples 900: Deleted 0. Elapsed 0/0 sec.
NOTICE:  Rel beruf: Pages: 18 --> 10.
NOTICE:  BlowawayRelationBuffers(beruf, 10): block 11 is referenced
(private 0, last 0, global 1)
FATAL 1:  VACUUM (vc_vacheap): BlowawayRelationBuffers returned -2

what exactly does that mean? how do you recover from this? would i lose
data if i dump the data from this table and recreate it?

thanks

frank