vacuum error

I am seeing the following error in pgsql 8.1.2:

2007-03-05 10:00:51.106 PST [9834]    DEBUG:  vacuuming "pg_toast.pg_toast_1260"
2007-03-05 10:00:51.106 PST [9834]    DEBUG:  index "pg_toast_1260_index" now contains 0 row versions in 1 pages
2007-03-05 10:00:51.106 PST [9834]    DETAIL:  0 index pages have been deleted, 0 are currently reusable.
        CPU 0.00s/0.00u sec elapsed 0.00 sec.
2007-03-05 10:00:51.106 PST [9834]    DEBUG:  "pg_toast_1260": found 0 removable, 0 nonremovable row versions in 0
pages
2007-03-05 10:00:51.106 PST [9834]    DETAIL:  0 dead row versions cannot be removed yet.
        There were 0 unused item pointers.
        0 pages are entirely empty.
        CPU 0.00s/0.00u sec elapsed 0.00 sec.
2007-03-05 10:00:51.106 PST [9834]    DEBUG:  vacuuming "pg_catalog.pg_statistic"
2007-03-05 10:00:51.107 PST [9834]    ERROR:  could not access status of transaction 3229475082
2007-03-05 10:00:51.107 PST [9834]    DETAIL:  could not open file "pg_clog/0C07": No such file or directory

What does it mean, and what should I do about it?

TIA.
Ed