VACUUM possible bug

Hi to all,

After upgrading to 7.1, I have noticed that when doing a vacuum, the
postmaster usually crashes.  Noticed also that the available space is 0
bytes free.  The pg_xlog directory then contains a large number fo
WAL-files.   Tables size are about 7GB for a total database size of over
50GB.

Question is why do the WAL-files increase during the VACUUM ?  I normally
have aroung 15GB free space on the drive, so even if a table is re-copied,
there should still be space ?

Does not vacuum commit after each table, or does it commit after the whole
operation ?  If so, is it possible to make vacuum commit after each table
(without doing it manually by vacuuming one table at a time) ?

I'm currently upgrading to 7.1.2, maybe the bug has been fixed in this
version.

Thanks
Robert